By Z. Rakus. Nazarene Bible College. 2019.
They may epitol 100mg fast delivery, however cheap 100mg epitol otc, come for treatment when urged by a partner or in the aftermath of traumatic events cheap 100mg epitol. Counterphobic individuals are psychologically organized around defenses against their fears. They may seek out dangerous situa- tions, thrive on risk, and have a reputation for unnerving calm in the face of peril. Having disowned and projected their own anxieties, they evoke anxious countertrans- ferences in therapists, who see the realistic dangers in their risk taking. It is critical to work slowly with them and to tolerate their bravado for some time before beginning to push them to acknowledge even normal fear, much less neurotic anxiety. In all patients for whom anxiety is pervasive, there may be a period in treatment in which they suf- fer a depressive reaction to giving up some of the magical ideas that accompany their anxiety- driven psychology. Characteristic pathogenic belief about self: “I am in constant danger that I must somehow elude. Personality Syndromes—P Axis 39 Obsessive–Compulsive Personalities Individuals with obsessive–compulsive personalities are emotionally constricted and regimented. They prefer to operate as if emotions were irrelevant and to defend against threatening emotions and desires through rigidity, regimentation, and intellectualiza- tion. They tend to be excessively concerned with rules, procedures, order, organiza- tion, schedules, and so on, and may be excessively devoted to work and “productiv- ity” to the detriment of leisure and relationships. They rely on intellectualization as a defense and tend to see themselves as logical and rational, uninfluenced by emotion. Beneath an “orderly” and regi- mented exterior, they are preoccupied with underlying issues of control, and caught in an unconscious conflict between feeling that they must submit to others’ demands (which elicits rage and shame) or rebel and defy them (which elicits anxiety and fear of retaliation). Rigidity, order, and intellectualization defend against awareness of the underlying conflict and the emotions that accompany it. Central to an obsessive–compulsive psychology is a resistance to feeling “out of control. Freud (1913) became impressed with the similarity of the stubborn, punctilious, and hoarding tendencies of the obsessive–compulsive adult to a resistant child’s response to toilet training—a leap that captured the imagination of his contemporaries and gave us the word “anal” as a descriptor of this psychology. He associated a tendency toward this character style with high levels of temperamental aggressiveness, which may make toilet training a struggle, but which also may intensify any situation in which a child is required to exert control over impulses and desires (eating, sexuality, general obedi- ence). Parents with controlling tendencies may contribute to this character style and to its characteristic conflicts between giving versus withholding, generosity versus self- ishness, and compliant submission versus oppositional defiance. People with obsessive–compulsive personalities, evocatively described by Reich (1933/1972) as “living machines,” seem to have identified with caregivers who expected them to be more grown-up than was possible at their age. They regard expressions of most affects as “immature,” they overvalue rationality, and they suf- fer humiliation when they feel they have acted childishly. Only when an emotion is logically defensible or morally justified—for example, righteous anger—do they find it acceptable. Psychoanalytic scholarship (Fisher & Greenberg, 1985; Salzman, 1980; Shap- iro, 1965) suggests that people with obsessive–compulsive personality styles fear that their impulses, especially their aggressive urges, will get out of control. Most obses- sive thoughts and compulsive actions involve efforts to undo or counteract impulses toward destructiveness, greed, and messiness. Because guilt over unacceptable wishes is severe, the conscience of a pathologically obsessive–compulsive person is famously rigid and punitive. Self-criticism is harsh; such individuals hold themselves (and others) to ideal standards. They follow rules literally, get lost in details, and postpone making decisions because they want to make the perfect one. They are scrupulous to a fault, but may have trouble relaxing, joking, and being intimate. Although obsessive and compulsive qualities express similar unconscious preoc- cupations and hence appear together, some people exhibit obsessional features with little compulsivity, while others exhibit compulsive features with little obsessional- ity. Obsessive people are chronically “in their heads”: thinking, reasoning, judging, 40 I. Compulsive souls are chronically “doing and undoing”: cleaning, collect- ing, perfecting. Obsessive patients are ruminative and cerebral; their self-esteem may depend on thinking. Compulsive individuals tend to be busy, meticulous, perfectionis- tic; their self-esteem depends on doing. In therapy, an individual with an obsessive–compulsive personality may try hard to be cooperative but covertly resist the therapist’s efforts to explore the patient’s affec- tive world. The patient may become subtly oppositional, expressing unconscious oppo- sition by coming late, forgetting to pay, and prefacing responses to the therapist’s com- ments with “Yes, but. To the clinician, the relationship may feel subtly (on not so subtly) like an ongoing power struggle. As the patient insists on tendentious argument rather than more authentic emotional engagement, the therapist may become impatient and exasperated. Effec- tive therapy requires sustained and patient exploration of those aspects of personality that individuals with obsessive–compulsive personalities otherwise spend inordinate energy trying to subdue. Central tension/preoccupation: Submission to versus rebellion against control- ling authority. Characteristic pathogenic belief about self: “Most feelings are dangerous and must be controlled. Schizoid Personalities The term “schizoid” may be among the more confusing in the clinical literature because the same term has been used to describe markedly different psychologies. Some may have subsyndromal schizophrenia spectrum disorders in which “negative symptoms” predominate (e. Westen and colleagues (2012) empirically identified a grouping of patients in a clinical sample that they labeled “schizoid–schizotypal,” characterized by “pervasive impoverishments, and peculiarities in, interpersonal relationships, emotional experi- ence, and thought processes” (p. Personality Syndromes—P Axis 41 Although this deficit-based version of “schizoid” may be more familiar to clini- cians, psychoanalytic writers have observed and described a different psychology to which they have also applied the term “schizoid. Here we focus on the less familiar personality syn- drome described by psychoanalytic writers, and simply note that the term “schizoid” has been used differently in the broader clinical (especially psychiatric) literature. Individuals with schizoid personality styles easily feel in danger of being engulfed, enmeshed, controlled, intruded upon, overstimulated, and traumatized—dangers that they associate with becoming involved with other people (Klein, 1946). They may appear notably detached, or they may behave in a socially appropriate way while pri- vately attending more to their inner world than to the surrounding world of human beings (Fairbairn, 1952). Some schizoid individuals withdraw into solitary environ- ments and even hermit-like reclusiveness; others retreat in more psychological ways to the fantasy life in their minds (Winnicott, 1971). Although seriously schizoid individuals, especially those with schizotypy, may appear indifferent to social acceptance or rejection, to the extent of having eccentrici- ties that serve to put others off, this apparent indifference may have more to do with establishing a tolerable level of space between themselves and others than with igno- rance of social expectations; in this way, they differ significantly from individuals on the autism spectrum (Ridenour, 2014). The clinical literature is mixed about whether to view schizoid psychology from the perspective of conflict (between closeness and distance needs) or from that of deficit (developmental arrest that precluded the achieve- ment of interpersonal relatedness). We suspect that both kinds of schizoid psychologies can be found across the health-to-illness spectrum, with the more conflicted version characterizing schizoid individuals in the higher-functioning ranges. Schizoid individuals are often seen as loners and tend to be more comfortable by themselves than with others. At the same time, they may feel a deep yearning for close- ness and have elaborate fantasies about emotional and sexual intimacy (Doidge, 2001; Guntrip, 1969; Seinfeld, 1991).
It is important ofen employs their own ‘best guess’ strategy based on to recognize that the resultant patern of behavior afer limited evidence and on their own experience in utiliz- brain damage will vary enormously based on diﬀerences ing these strategies discount epitol 100 mg with mastercard. Most teams utilize a management in etiology epitol 100 mg lowest price, extent epitol 100mg with visa, size and site of the insult, along with strategy that includes systemic hypothermia combined variations in subject age, sex, education, etc. Our ability to with topical cooling of the head, avoidance of cerebral recognize a patern of change will also vary, even though hyperthermia during rewarming and in the immediate the lesion may be the same, dependent on how and with post-operative interval, maintenance of normal or even what tools the assessment is performed. Consensus regarding traditional clinical setings where neurobehavioral assess- other issues — including clinical assessments of the ment is performed routinely, the cardiac surgery environ- role of hyperoxia, pH-management, optimal hemat- ment is diﬀerent. Where usually the examiner’s time is ocrit, pharmacological agents, and anti-inﬂammatory not restricted, the time available to assess cardiac patients and leukocyte suppression strategies — continues to be may ofen be less than 60 minutes, especially pre-opera- lacking. In many clinical setings, the assess- comes associated with aortic arch surgery is still evolving. The surgery, however, the assessment is ofen able to occur incidence of these complications depends upon the com- before and afer surgery, albeit restrained by time and the plex interplay between the pre-existing pathological sta- physical condition of the patient. It is not possible strategies deployed to minimize complications, as well to exhaustively, evaluate all cognitive domains nor all as how we measure and report the complications that do the changes that may occur. Before examin- important as the choice of what tests are performed is ing these outcomes, a brief synopsis of neurobehavioral the decision on how the results will be collated, exam- assessment as it has been utilized in cardiac surgery will ined and reported. This has provided a common entry point for study in the diﬃcult area; however, it has been by no means fully embraced by Neuropsychological testing investigators. The consensus meeting addressed some major issues including the choice of tests, method of Negative eﬀects of aortic arch surgery on the brain have reporting, changing the inﬂuence of repetitive testing always been recognized, however, there are few early (test-retest reliability) and the inherent limitations of reports on neurobehavioral deﬁcits. The aim of neurobehavioral assessment is diﬀerent from that of neurological assess- In general, the use of neuropsychological testing method- ment. The focus has been on standardizing cardiac literature [20−26], it must be recognized that they the delivery and interpretation of assessments and ﬁnd- do not cover all domains and, consequently, we remain ings, rather than on exploring the interactions result in ignorant of functions that are untested and their contri- the changes that have manifested. Instead, broad range of techniques, along with integration of his- assessment bateries are designed to meet the needs of tory and clinical ﬁndings, to allow appropriate interpreta- local investigators. While it is important to recognize that the Speciﬁc and detailed explanations of individual tests ‘neuropsychological examination cannot be properly con- utilized to detect changes in diﬀerent cognitive domains ducted or interpreted either in a vacuum or in an isolated may be found elsewhere . An example of a test bat- manner’ , the role and signiﬁcance of these assess- tery (and the domains investigated) commonly used in ments in the surgical seting may at times have minimized cardiac surgical patients is: Rey Auditory Verbal Learning this consideration. It is necessary, therefore, to understand and Non-verbal Memory (memory functioning); Trail the reason for performing neurobehavioral assessment Making Tests A and B, Leter Cancellation Task, Symbol- in the surgical arena. This was recognized as an issue at the original consensus meeting in 1994, and the subject of a follow-up publication in 1997, Choice of test battery entitled approach to ‘Deﬁning dysfunction’ . Despite In the context of cardiac surgery, neurobehavioral assess- this interest, and a genuine atempt in the literature to ment tends to be limited by a variety of external factors adequately explore the methods of analysis, a common including assessment time, the interval prior to surgery that approach to analysis is not in practice [21,28,29]. This assessment design intro- as a decrease of at least 20% on two or more of the neu- duces its own constraints related to the application of the ropsychological tests performed from the pre- to post- test instruments on multiple occasions. Other methods to deﬁne change The consensus group atempted to introduce a include the use of one or two standard deviations, or the core batery of tests to promote the ability to compare use of 20% change in 20% of the tests administered. Indeed, for some methods, including Outcomes of aortic arch surgery the reliable change index, a control group is necessary to allow the index to be calculated. Diﬀerent investigators Neurological deficits have atempted to mandate the use of speciﬁc types of controls. This Other groups have preferred a surgical cohort undergo- group identiﬁed three distinct neurological end points ing alternate surgeries , or patients with similar dis- following surgery: temporary neurological dysfunction ease managed non-surgically . As ranging from simple confusion (grade 1) through to overt such, it is important not to look at tests in isolation but psychosis (grade 4) and parkinsonism (grade 5) . While most of the data published, both examine diﬀerent areas of brain function and help identify contemporary and historical, has been observational or damaged areas is implicit in their design. However, inter- retrospective in nature, such data does provide an impor- pretation of paterns of function or change to identify spe- tant baseline for prospective evaluation. Speciﬁcally, the subtleties that are inherent to any change following brain Hypothermic circulatory arrest damage tend to be overlooked when patient outcomes are dichotomized. Our choice of assessment tools can 200 patients operated on between 1985 and 1992. Only the presence of pre-operative the method of brain protection did not inﬂuence neuro- neurological symptoms was independently predictive of logical outcome. Signiﬁcantly, Group using data from on 228 patients operated on in acuteness of operation was identiﬁed only as a univari- 49 centers from 1986 to 1992, found a 20. Permanent neurological deﬁcits accounted for 27 tiﬁed as a univariate risk factor for the development of (11. This and extended cardiac ischemic time (>120 minutes) and paper supported the independent risk factors for stroke rupture as predictors of overall neurological dysfunction. In an earlier study by the ences in confounding factors between the groups, including same authors, they reported a 16. Speciﬁcally, they (from acute dissection) were independent predictors of noted that extended bypass time was predictive of stroke; temporary deﬁcit, and the presence of old cerebral infarc- this ﬁnding is supported by other authors . Moon and Sundt , reporting on a small relationship between duration of cerebral perfusion and group of 72 patients undergoing aortic arch surgery for overall neurological dysfunction of any type. There is deﬁnite justiﬁcation for the adoption of the descending aorta having a mortality of 36. The There are only a limited number of studies compar- approach of Svensson et al. While the interpretation of this study diverse deﬁnitions of temporary or transient neurological is limited by the choice of neurobehavioral assessment deﬁcits has made interpretation between diﬀerent studies tool (Mini-Mental State Examination), and small study problematic [40,59,63]. Nevertheless, the early reports by size, they did prospectively report 60 consecutive patients Svensson et al. They utilized a mul- while they were not able to demonstrate any variation in tiple test batery and compared their ﬁndings to an the diﬀerent Mini-Mental Status Examination scores (i. They reported deterioration in the patients compared patients with transient brain dysfunction were more likely with normative data on all measures; notably the level of to have a larger decline of memory than those without. They presented neurological sequelae, they demonstrated that increased excellent results with 2% mortality and stroke rates and age (age >70 years) and an atherosclerotic aneurysm an incidence of only 2. As such, in those patients with neurobehavioral deﬁcits than the lack of support for these ﬁndings in the literature those without (50% vs. The small sample size, however, late outcome (median 54 days, range 16−129 days), and makes any atempt to interpret group diﬀerences imprac- the inﬂuence of duration of circulatory arrest. Interestingly, they found no deﬁcits following a test batery that allowed examination of 5 domains surgery when they used the commonly reported meth- (atention, processing speed, memory, executive func- odology of deﬁning decline as one standard deviation tion and ﬁne motor function), they analyzed both group or 20% decline in 20% of tests used. They performed a detailed neurobehavio- observational study using the Wechsler Adult Intelligence ral assessment (memory, atention, concentration, psy- Scale-revised, administered pre-operatively, and at 2−3 chomotor performance, higher cortical function) at 6, 12 weeks and 4−6 months post-operatively. Signiﬁcant dete- and 24 weeks, and reported both dichotomous outcome rioration was observed in digital span, the arithmetic and (impairment deﬁned as a 20% decline in two or more picture completion subtests at the early testing period, with tests), and group z-scores. Unfortunately, as mandated digit symbol showing deterioration in the later follow-up.
It is caused by free oxygen radical Radiologically bilateral reticulonodular shadows damage to alveolar epithelial and capillary endo- with bilateral pleural effusions are seen purchase epitol 100mg without a prescription. Other than the temporal relation to the darone induced pneumonitis is diagnosed more causative drugs quality epitol 100 mg, there are no clinical or radiological easily by Gallium scintigraphy which helps to Drug-induced Respiratory Diseases 361 exclude primary cardiac arrythmias as a cause for thromboembolism is to discontinue heparin and radiological opacities and clinical symptoms like institution of anti-vitamin K treatment order epitol 100 mg with amex. The onset of toxicity is within few damage occurs is as follows: hours to few days. Hypersensitivity reaction: It is an immunological noncardiogenic pulmonary edema with predominant mediated lung disease presenting as pneumonitis neutrophil infiltration. Serum IgE and syndrome or alveolar hemorrhage is common positive skin tests to the offending drug confirms complication with D-penicillamine and has high the diagnosis. Oxidants: Lung damage occurs through free lazine, Procainamide, Chlorpromazine, D-penicilla- oxygen radicals and presents as pneumonitis. Altered collagen production: Collagen induced lung skin, kidney, blood involvement with antihistone damage either due to increased production or antibodies detected in the serum. The above drugs reduced degradation of collagen, clinically also cause mediastinal lymphadenopathy. Lipidosis: Crystalloid phospholipases intra-cellular iatrogenic pulmonary edema is also known. In or cytoplasmic inclusion bodies cause cell certain drugs like Mitomycin, Busulphan , Procar- damage. Clinically reversible interstitial lung bazine, Bromocryptine and Methysergide unilateral involvement also associated with multiorgan or bilateral pleural effusions either acute or chronic involvement. Lupoid reaction: Autoantibody induced lung is usually exudative with lymphocytic predominance damage occurs in cases with personal predis-. Drugs like oral steroid cause iatrogenic Clinical suspicion can be made depending on the Cushings which leads to mediastinal lipomatosis, presence of certain symptoms like fever , breathless- Methysergide causes mediastinal fibrosis which may ness, bronchospasm, lupus like presentation as lead to superior vena caval obstruction. High index of clinical Pulmonary vascular involvement: Pulmonary suspicion is very important for early diagnosis of hypertension leading to right heart failure caused drug induced respiratory disorders, but sometimes by appetite suppressant Aminorex occurs usually in it is very difficult to find out the exact site of lung 6 to 12 percent of cases. Proper correlation of clinicoradiological manifes- Pulmonary thromboembolism is known during tations with history of drug ingestion, e. Radiological correlation is very easy and non- • Acebutolol invasive but not all cases show positive cor- • Amiodarone relation, i. Pneumonitis and fibrosis: Appears like usual • Sulphasalazine interstitial pneumonia with predominant basal subpleural distribution. Role of High Resolution Computerized Tomo- this results in diffuse airspace consolidation graphy Scan of lung: that may have a dependent distribution. Ground glass pattern suggestive of pneumonitis logical drug and symptomatic treatment if neces- b. Usually, drug induced respiratory disorders reverse but sometimes corticosteroids are required to prevent further progression as well as to cure, D. Drug induced lung monoxide diffusion capacity (D ) in Bleomycin disease; 1990 review. High For example, granulomatous pneumonitis seen in Resolution Computerized Tomography of Drug induced methotrexate lung hazards. Shailly Saxena, Bavin M Shah, Jyotsna M Joshi Pulmonary Hydatidosis andPulmonary Hydatidosis andPulmonary Hydatidosis andPulmonary Hydatidosis andPulmonary Hydatidosis and 20 Pleuropulmonary AmoebiasisPleuropulmonary AmoebiasisPleuropulmonary AmoebiasisPleuropulmonary AmoebiasisPleuropulmonary Amoebiasis 20. Unilateral multiple foci are reported in 20 percent patients as most patients harbor only Cystic hydatid disease is a zoonotic infection of one solitary cyst with single organ involvement tapeworms of genus Echinococcus and species (80%). The frequency of cyst in the Various radiological signs are seen in case of hydatid literature is as follows: liver 60 to 75 percent, lung cyst of the lung depending whether the cyst is 15 to 25 percent and remaining parts of the body ruptured or not (Table 20. Central unruptured 10 to 15 percent including mediastinum, brain and cysts may present, as round homogenous nodular bone. Ruptured cyst produces several radiological appearances, as the The progressive growth of the cysts, their tendency cyst enlarges and comes in communication with the to erode the organs and tissues with which they bronchus, air may enter between the pericyst and come in contact, their infectivity and the existence the ectocyst which appears as a thin lucent crescent of intrathoracic pressure could explain the unusual in the upper circumference referred to as Crescent evolution of the cyst in the hepatic dome. Sometimes double crescent cyst of the lung can be located in any pulmonary shaped lucencies may be seen between the pericyst lobe and can consist of multiple foci in one or both and ectocyst, ectocyst and endocyst called as Double lungs. If the cyst itself ruptures and attacked area of the lung due to abundance of blood air enters the cyst outlined by double arch known flow to this area compared to other lobes of lung. Collapsed • Double arch of Ivanissevich membrane of parasite may give rise to radiological • Cumbo sign • Onion peel sign appearances described as serpent or snake sign (Fig. Polycyclic calcification when both mother and daughter cyst are calcified within the chest wall. A crushed eggshell sunburst appearance of calcification may result from prior rupture and Fig. Rarely daughter cyst may give appearance Treatment of “Rising sun” in the lower part of cavity. Response to medical therapy abscesses and fistulous tract can be picked up and is related to the thickness of the cyst wall, which hydatid cyst with detached membrane is seen with the drug must penetrate to reach the germinal layer, great precision. Surgery includes complete excision of the disease process with maximum preservation of the lung tissue, most authors advocate conser- vation of the lung parenchyma, reserving resection for ruptured cysts that result from destruction or infection of the adjacent tissue. Every patient who has hydatid cyst in the lung should be investigated for associated cyst in the liver. This procedure is usually reserved in patients where other methods have failed or in inoperable patients. Transdia-phragmatic Thoracic Involvement in Hepatic Hydatid Disease Presenting as Pneumonitis Right Base: A Case Report and Brief Review of the Literature. It is the third most common into the bronchus with little infiltration of the manifestation of amoebiasis in the body and is parenchyma or sometimes a lung abscess may probably a morbid entity. The disease predominantly rupture into a bronchus thus establishing a occurs in 3rd or 4th decade and in males with the hepatobronchial fistula. Rarely a homogeneous mass lesions with ill-defined margins, bronchobiliary fistula may occur due to turbid fluid with low echoes and hepatomegaly. Due to also differentiates empyema, air pockets in pleura complicated symptomatology, the most important and subphrenic region. Transverse and saggital prerequisite in the diagnosis of such cases is a high windows help to locate the site and dimensions of index of suspicion, especially true in countries like the abscess. Hemoptysis often precedes show the primary abscess in liver with subphrenic expectoration of dark reddish-brown sputum that collection and the rent in the diaphragm if present. Past history of dysentery, localized pain and tenderness over the liver area, right shoulder pain or persistent hiccough all indicate concomitant hepatic and subphrenic involvement. Diagnosis Apart from hematology and serum biochemistry, radiological and microbiological investigations are mandatory for diagnosis and therapeutics. Serological tests like indirect hemmaglutination test and Enzyme linked immunosorbent assay for antigen detection may support an amoebic etiology. Chest roentgenograms shows elevation and loss of neatness of the diaphragm contours, basal pneumonitis, lung abscess, pleural effusion, hydropneumothorax, subphrenic air fluid level, hour glass abscess and flask shaped heart due to pericardial effusion, if present. Contrast studies like abscessogram with propyliodine will reveal extent of the disease, adhesions between live, Fig. Ultrasound will show lower lobe Pulmonary Hydatidosis and Pleuropulmonary Amoebiasis 369 The fistula is seen in an appropriate saggital Complications like subphrenic abscess and window.
Some care must be taken in deciding the length of the follow up period generic epitol 100 mg on line, which must be long enough for the disease to manifest cheap 100 mg epitol otc, but not so long that cases can arise after the original testing epitol 100 mg visa. Chest X-ray and sputum smears are used to determine the nature of pneumonia rather than lung biopsy with examination of the diseased lung tissue. Similarly, electrocardiograms and serum enzymes are often used to establish the diagnosis of acute myocardial infarction, rather than catheterization or imaging procedures. The simpler tests are used as proxies for more elaborate but more accurate ways of establishing the presence of a disease, with the understanding that some risk of misclassification exists. But simpler tests are only useful when the risks of misclassification are known and found to be acceptably low. Without all these data, it is not possible to assess the risks of misclassification. Given that the goal is to fill in all four cells, it must be stated that sometimes this is difficult to do in the real world. It may be that an objective and valid means of establishing the diagnosis exists, but it is not available for the purposes of formally establishing the properties of a diagnostic test for ethical or practical reasons. Consider the situation in which most information about diagnostic tests is obtained. Under these circumstances, physicians are using the test in the process of caring for patients. They feel justified in proceeding with more exhaustive evaluation, in the patient’s best interest, only when preliminary diagnostic tests are positive. They are naturally reluctant to initiate an aggressive workup, with its associated risks and expenses, when the test is negative. As a result, information on negative tests, whether true negative or false negative, tends to be much less complete in the medical literature. The researchers understandably were reluctant to subject men to an uncomfortable procedure without supporting evidence. The clinical manifestations were described nearly a century ago, yet there is still no better way to substantiate the presence of angina pectoris than a carefully taken history. Certainly, a great many objectively measurable phenomena are related to this clinical syndrome, for example, the presence of coronary artery stenosis seen on angiography, delayed perfusion on a thallium stress test, and characteristic abnormalities on electrocardiograms both at rest and with exercise. But none is so closely tied to the clinical syndrome that it could serve as the standard by which the condition is considered present or absent. The validity of a laboratory test is established by comparing its result to a clinical diagnosis based on a careful history of symptoms and a physical examination. Once established, the test is then used to validate the clinical diagnosis gained from history and physical examination. An example would be the use of manometry to ‘confirm’ irritable bowel syndrome, because the contraction pattern demonstrated by manometry and believed to be the characteristic of irritable bowel syndrome was validated by clinical impression in the first place. They must choose as their standard of validity another test that admittedly is imperfect but is considered the best available. Just such a situation occurred in a comparison of real-time ultrasonography and oral cholecystography for the detection of gallstones. In five patients, ultrasound was positive for stones that were missed on cholecystography. Two of the patients later underwent surgery and gallstones were found, so that for at least those two patients, the standard oral cholecystogram was actually less accurate than the newer real-time ultrasound. Similarly, if the new test is more often negative in patients who really do not have the disease, results for those patients will be considered false negatives compared with the old test. Thus, if an inaccurate standard of validity is used, a new test can perform no better than that standard and will seem inferior when it approximates the truth more closely. A simple way of looking at the relationships between the test results and the true diagnosis (by Gold Standard) is shown in Table. The test is considered to be either positive (abnormal) or negative (normal) and the disease either present or absent. There are then four possible interpretations of test result, two of which are correct, and two wrong. Thus when a gold standard is available, the categorization of test results into ‘true positives’ (disease present by both the tests), ‘false positives’ (disease present only by the test but not by the gold standard), ‘true negatives’ (disease absent by both the tests) and ‘false negatives’ (disease absent by the test but present by the gold standard) is best done by constructing a 2 × 2 table (Table 7. From the table the following statistical parameters of diagnostic accuracy can be calculated: 1. However, there are several other criteria, which need to be taken into consideration while choosing optimal sensitivity of a test. Positive a = 27 b = 35 a + b = 62 Negative c = 10 d = 77 c + d = 87 Total a + c = 37 b + d = 112 a + b + c + d = 149 positive” result. In other words, 31 percent of non-diseased people screened by the test (clinical diagnosis) will be wrongly classified as “diseased” when they are not. Use Specific tests are useful to confirm (or “rule in”) a diagnosis that has been suggested by other data. This is because a highly specific test is rarely positive in the absence of disease—that is, it gives few false positive results. For diseases like diabetes for which treatment does not markedly alter outcome, specificity must be high and early cases may be missed, but false positives should be limited; otherwise the health system will be overburdened with diagnostic demands on the positives, both true and false. Highly specific tests are particularly needed when false positive result can harm the patient physically, or financially. Thus before patients are subjected to cancer chemotherapy, with all its attendant risks, emotional trauma, and financial costs, tissue diagnosis is generally required instead of relying upon less specific tests. That is, high specificity is necessary when false positive errors must be avoided. Bias Sometimes the sensitivity and specificity of a test are not established independently of the means by which the true diagnosis is established leading to biased assessment of the test’s properties. As already mentioned, if the test is evaluated using data obtained during the course of a clinical evaluation of patients suspected of having the disease in question, a positive test may prompt the clinician to continue pursuing the diagnosis, increasing the likelihood that the disease will be found. On the other hand, a negative test may cause the clinician to abandon further testing making it more likely that the disease if present will be missed. In other situations, the test result may be part of the information used to establish the diagnosis or conversely, the results of the test may be interpreted taking other clinical information of the final diagnosis into Research on Diagnostic Tests 75 account. Because X-ray interpretation is somewhat subjective, it is easy to be influenced by the clinical information provided. All clinicians experience the situation of having X-rays over read because of a clinical impression, or conversely, of going back over old-X-ray in which a finding was missed because a clinical event was not known at the time and therefore attention was not directed to the particular area in the X-ray. Because of these biases, some radiologists prefer to read X-rays twice, first without and then with the clinical information. All of these biases tend to increase the agreement between the test and the standard of validity. Chance Values for sensitivity and specificity (or likelihood ratios and other characteristics of diagnostic test discussed later in this chapter) are usually estimated from observations on relatively small sample of people with and without the disease of interest. Because of chance (random variation) in any one sample, particularly if it is small, the true sensitivity and specificity of the test can be misrepresented, even if there is no bias in the study. The particular values observed are compatible with a range of true values, typically characterized by the ‘95% confidence interval’. The width of this range of values defines the degree of precision of the estimates of sensitivity and specificity.
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