Predictive Value Of Positive Test Research Articles

Fetal macrosomia: predictive value of maternal glycaemic profiles, oral glucose tolerance tests and ultrasound measurements

SummaryThe accuracy of glucose tolerance tests, glycaemic profiles and sonographic measurements at 32 weeks in the antenatal diagnosis of fetal macrosomia was evaluated in 38 euglycaemic and 30 gestational diabetic pregnant women.The predictive value of positive tests was low (glucose tolerance 17 per cent, glycaemic profile 16 per cent, ultrasound measurements 27 per cent), but each of them was useful in excluding macrosomia, with predictive values of negative tests of 76, 74 and 81 per cent respectively.The combination of all three tests led to an increase in sensitivity (71 per cent), but had a substantially unchanged predictive value (positive 19 per cent, negative 71 per cent).

Sensitivity and specificity of the histamine challenge test for the diagnosis of asthma in an unselected sample of children and adolescents

The purpose of this investigation was to study factors of importance for the degree of bronchial responsiveness and, furthermore, to evaluate the sensitivity, specificity and predictive value of a bronchial challenge test with histamine for the diagnosis of asthma in 495 randomly selected children and adolescents, aged 7-16 yrs, from Copenhagen, Rigshospitalet. Detailed history about allergic symptoms, physical examination and bronchial histamine challenge tests were performed at the out-patient clinic. Asthma, atopic disease and height were found to be of great importance for the degree of bronchial responsiveness, whereas the age, sex and smoking habits were of no significance. The percentage of asthmatics with bronchial hyperresponsiveness, i.e. sensitivity to the test, increased towards 100% on inhaling increasing concentrations of histamine, but this was accompanied by a decrease in specificity and predictive values of positive test in regard to the diagnosis of asthma. However, lower concentrations of histamine may be preferable in order to distinguish between asthma and non-asthma in population samples, as inhalation of 2.4 mg.ml-1 and provocative concentration producing a 20% fall in forced expiratory volume in one second (FEV1) (PC20) provided an acceptable sensitivity (57%), specificity (98%), and predictive value of a positive test (60%). We conclude that as regards the diagnosis of asthma, a low predictive value confirms that the bronchial challenge test plays only a supplementary, but valuable, role in detecting the disease in population samples.

Faut-il dresser un bilan de coagulation avant une anesthésie locorégionale chez un sujet ASA 1 ?

Coagulation testing is warranted before regional anaesthesia to avoid bleeding complications. The most feared is spinal epidural hematoma causing neurologic deficits if epidural or spinal anaesthesia is performed in patients with hemostatic defects. These concepts are submitted to critical appraisal in the special setting of ASA class 1 patients. If patients are correctly assessed by questionnaire and physical examination as having negative history, asymptomatic coagulopathies are very scarce, mainly represented by hemophilia in men and von Willebrand's disease in women. Activated partial thromboplastin time (APTT) is the main test to assess coagulation defects. APTT is not sufficiently sensitive to identify all patients with coagulopathies, especially mild ones and von Willebrand's disease. Medium specificity combined with low prevalence of the disease to be screened incur false positive results and poor predictive value of positive tests as well for diagnostic purpose as for prognostic evaluation of haemorrhagic risk. Neurologic deficits secondary to compression by haematoma are rare and their frequency presently unknown. Epidural or spinal anaesthesia has been shown to be quite safe when performed in patients with various hemostatic abnormalities. Consequently, routine coagulation testing in ASA class 1 patients seems to provide more drawback than benefit. Lack of coagulation testing prior to regional anaesthesia is probably not a factor of increased risk if patients are correctly assessed.

99mTc plasmin in 394 consecutive patients with suspected deep venous thrombosis

Three hundred and ninety four consecutive out-patients with suspected deep venous thrombosis (DVT) were investigated with the 99mTc-plasmin test and physical examination and 307 of them with phlebography. Fresh thrombi were present in 124 patients and the plasmin test was pathological in 118 of these (sensitivity 95%). The thrombi that were missed were all located below the knee and measured less than 10 cm on the phlebographic films. The predictive values of negative and positive tests were 91% and 49%, respectively. The predictive value of a positive test was higher with an increasing number of measuring points with a pathological uptake. To get the final result, a single series of measurements 5 min after injection was sufficient. If clinical signs of inflammation were present. the plasmin test was usually pathological. Median time for the plasmin test to become normal during anticoagulant therapy was 14 days for calf DVT and 6 months for proximal DVT. The plasmin test was found to be useful as a screening test in patients without extensive signs of inflammation in the legs. It has a high sensitivity even in patients with long-standing symptoms.

Comparison of methods for diagnosing bacterial vaginosis among pregnant women

The diagnosis of bacterial vaginosis is usually based on clinical criteria including homogeneous vaginal discharge, an elevated vaginal pH, the presence of clue cells, and an amine odor. We have evaluated the vaginal flora and clinical signs for 593 pregnant women. Gardnerella vaginalis, Bacteroides spp., and Mycoplasma hominis were isolated more frequently among women with clinical signs than among those without clinical signs of bacterial vaginosis in multivariable analyses that controlled for other bacteria. To determine the laboratory method that best predicted bacterial vaginosis, we calculated the sensitivity, specificity, and predictive value of positive and negative tests for Gram-stained vaginal smears, gas-liquid chromatography of vaginal fluid, and G. vaginalis cultures compared with clinical signs. G. vaginalis culture was sensitive (92%) and both gas-liquid chromatography (78%) and Gram-stained vaginal smears (62%) were moderately sensitive in identifying women with three of the four clinical signs of bacterial vaginosis. However, the Gram-stained vaginal smear (95%) was more specific than G. vaginalis culture (69%) or gas-liquid chromatography (81%). The predictive value of a positive test was also higher for the Gram staining (76%) than for G. vaginalis culture (41%) or gas-liquid chromatography (48%).

Streptococcal Pharyngitis Study

Redd and co-workers found the sensitivity of their rapid diagnostic test for group A streptococcal pharyngitis to be 62.8% and its specificity to be 96.9%. Furthermore, the positive predictive value of the test was determined to be 91.5%, sufficiently high to significantly influence the care provided to their patients. We strongly disagree with the authors' conclusion that their findings can be extrapolated to the general pediatric setting. Bayes theorem clearly relates a test's positive predictive value to its sensitivity as well as to the prevalence of true disease in the population.

Lactate dehydrogenase isoenzyme patterns in bovine liver tissue.

Liver lactate dehydrogenase (LDH) isoenzymes in normal and diseased cows were analyzed electrophoretically. This method (histoelectrophoresis) was improved for the direct analysis of tissue LDH isoenzymes. The mean values of LDH 1 through LDH 5 in the livers of normal cows were 31.7, 24.8, 27.3, 12.8, and 3.3%, respectively. In cases with hydropic degeneration of the liver, the patterns revealed increases of LDH 1 and LDH 2 as compared to normal cows. The patterns showed a decrease of LDH 1 and an increase of LDH 2 in fatty change of the liver. Congestion of the liver alone decreased LDH 1 and increased LDH 3, LDH 4 and LDH 5. Necrosis of the liver decreased LDH 1 and LDH 2, and increased LDH 3, LDH 4 and LDH 5. It was suggested that the functional hepatocellular damage due to anoxia might be a important factor of the change of liver LDH isoenzyme patterns. We have attempted to standardize the LDH isoenzyme patterns by using a computer under various conditions. In cases with hydropic lesions, the diagnostic sensitivity (DS) was 53% (28 of 53 cases) and the predictive value of positive tests (PVPT) was 100% (28 cases of 28 cases selected). In cases with congestive or necrotic lesions, DS was 41% (9 of 22 cases) and PVPT was 69% (9 cases of 13 cases selected).

Immunoscintigraphy of melanoma using radiolabelled antibodies: Pilot, prospective studies and Italian multicenter clinical trials

The studies on radioimmunodetection of malignant melanoma reported are based on the use of the 225.28S monoclonal antibody against a high molecular weight melanoma associated antigen, an IgG2a isolated and characterized by Ferrone et al. The strategy followed by us to check the characteristics and the behaviour of this antibody and to verify its possible use in clinical praxis, includes three groups of trials performed from 1982 to 1987. A pilot study was performed on 42 patients with 74 melanoma lesions, a multicenter study was realized, with the collaboration of 10 Italian nuclear medicine centers, on 254 patients with 539 lesions and prospective study performed on 44 patients with 54 suspected regional lymph nodes involvements. High sensitivity and specificity were obtained especially with the use of technetium compound which also allowed the attainment of very high predictive values of positive tests. No adverse reactions were noticed.

The predictive value of positive test results in screening for breast cancer by mammography in the Nijmegen programme.

After 10 years of screening for breast cancer by mammography in Nijmegen, the predictive value of positive screening results (PV+) was evaluated. The percentage of women with breast cancer in the group of referred women (PV+) for women under age 50 was 16-26%, regardless of the number of screening examinations they had. The percentage of women with breast cancer in the group of women who were biopsied was 25-40%, regardless of the number of examinations. For women aged 50 and over the predictive value was 34-57% and 58-90% respectively. It was further evaluated whether characteristics such as age, Quetelet index, parity, and Wolfe-classification could be used to increase the PV+ in women who were identified as positive by mammography. A logistic regression model analysis showed that true-positive and false-positive cases differ significantly only in terms of age and breast complaints. Although the model had a good fit, it could not be used to distinguish false-positive from true-positive test results.

Cerebrospinal fluid creatine kinase isoenzyme BB levels do not predict the clinical outcome in patients unconscious following cardiac resuscitation.

It has recently been claimed that an increase in creatine kinase isoenzyme BB(CK-BB) in cerebrospinal fluid (CSF) is well correlated with the cerebral outcome in patients resuscitated after cardiac arrest. Twenty-one such patients consecutively admitted from outside this hospital participated in the study. The patients were divided into two groups: 6 survivors and 15 nonsurvivors. The median CSF-CK-BB value was 5 U/L among nonsurvivors and below detection limit among survivors (NS). However, the predictive value of a positive test is limited, since only 6 of 15 nonsurvivors (40%) had an increase in CSF-CK-BB (predictive value of positive test = 67%). The predictive value of a negative test is limited, since 3 of 6 survivors (50%) showed no rise in CSF-CK-BB (predictive value of negative test = 25%). No relationship between cerebral dysfunction and CSF-CK-BB values was revealed. Thus, CSF-CK-BB does not predict the clinical outcome in patients resuscitated after cardiac arrest.

Rapid identification of Staphylococcus epidermidis.

A panel of Minitek sugar disks, consisting of trehalose, mannitol, xylose, and sucrose, was evaluated for its ability to identify blood culture isolates of Staphylococcus epidermidis (SE). Using a heavy suspension of organism in Mueller-Hinton broth, 50 microL was pipetted onto each disk in wells of a flat-bottomed microtiter tray. The tray was covered, incubated in a moist chamber in non-CO2 at 35 degrees C, and examined after 5 and 24 hours. A color change of yellow or orange was positive; no color change (red) was negative. Expected reactions for SE were as follows: negative trehalose, mannitol, and xylose; positive, sucrose. On evaluation of 227 coagulase-negative staphylococci (CNS) at 5 and 24 hours, the panel had a sensitivity of 94 and 96%, specificity of 92 and 89%, predictive value of positive tests of 97 and 96%, and predictive value of negative tests of 84 and 87%. This panel offered an inexpensive and convenient method for differentiating SE from the other CNS in five hours.

Screening of autopsy populations for previous occupational exposure to asbestos.

A screening procedure to select, in autopsy populations, subjects having a major likelihood of previous occupational exposure to asbestos is described. To test our necropsy population we searched for pleural plaques (PPs); the optical count of both lung asbestos bodies (ABs) and uncoated mineral fibers (UMFs) at least 10 microns in length was recorded. In the adult autopsy population studied in the Turin area, the predictive value given by a positive test for large-size PPs (mostly bilateral) was about 55%. This level of probability did not rise in relation to the AB counts, whereas an increase to over 75% was observed if more than 10,000 UMFs/g dry lung were present. In subjects without PPs or with small-size plaque lesions (mostly unilateral), predictive values of positive tests were 20 to 30% when ABs and UMFs were found to be below 100 and 10,000/g, respectively, and increased to approximately 40% if the AB count exceeded 500/g and to almost 70% for an UMF count above 100,000/g. In subjects without PPs or with small-size plaque lesions, the probability of being nonexposed was greater than 90% if neither ABs nor UMFs were found. This autopsy screening may be a reliable tool in selecting cases most probably related to occupational exposure.

Urinary enzyme analysis in renal allograft transplantation

The urinary excretion of four enzymes (fructose-1, 6-bisphosphatase, glutathione S-transferase, N- acetyl-β- d-glucosaminidase and pyruvate kinase) was assayed daily in 59 patients following renal cadaveric allografting. 51 patients were given cyclosporin A (CyA group) as an immunosuppressive, 8 patients were treated conventionally with azathioprine and prednisolone (CON-group). Urinary enzyme output was evaluated by two different mathematical models. Model A follows single enzyme excretion, whereas model B also analyzes enzyme patterns. The best results were obtained by a combined analysis of all four enzymes with model B. In the CON-group the sensitivity was 1.00, the specificity 0.85, the predictive values of positive test 0.45 and all 12 graft rejections were diagnosed correctly. In the CyA group the sensitivity was 0.40, the specificity 0.99, the predictive value of positive test 0.33, and 6 out of 9 rejections were recognized. The evaluation of the single enzymes did not produce similarly good results with either model.

Accuracy in Core Biopsy of the Prostate

In this autopsy study the predictive values of positive and negative tests of core biopsies of the prostate were investigated. Core biopsies, which were performed after evisceration, were compared with macroscopic and microscopic findings of the entire prostatic gland. Of 107 investigated patients, 100 contained prostatic tissue in the core biopsies. In 11 patients the core biopsies contained carcinoma. All these patients had carcinoma in the tissue sections from the prostate. In 89 patients the core biopsy did not contain carcinoma. 88 of these patients had no carcinoma in the tissue sections from the entire specimens. However, in 1 patient a highly differentiated acinar adenocarcinoma was found. From these results the predictive value of a positive test is 11/11 = 100%, and the predictive value of a negative test is 88/89 = 98.5%. Core biopsy is a suitable method in diagnosing prostatic diseases and gives a very high accuracy when the core biopsy contains prostatic tissue.

The erythrocyte aggregation value as a measure of the risk of myocardial infarction and arteriosclerosis of peripheral arteries.

The erythrocyte aggregation value (AW) has been determined in groups of patients with and without coronary heart disease (CHD) and in a group of apparently normal subjects, using the Metricell apparatus as described by Kachel et al. The following results were obtained: There was a close correlation between the AW and the existence of CHD or arteriosclerosis of peripheral arteries. The precision of the retrospective prediction of CHD by this noninvasive test in male subjects aged over 45 years (total CHD prevalence = 0.494) was: sensitivity = 0.571, specificity = 0.767. The predictive value of positive tests (PVpos) was 0.706, of negative test (PVneg) 0.647. The discriminatory ability of the AW test was superior to that of serum cholesterol determinations or measurement of other CHD risk factors made in the same population. The AW rises exponentially with the total score for risk factors for CHD hazard for the subject. It appears, however, from the insignificant correlations observed that there is no direct connection between the AW and any single risk factor.

Significance of human chorionic gonadotropin, alpha-fetoprotein, and pregnancy-specific beta-1-glycoprotein in the detection of tumor relapse and partial remission in 126 patients with nonseminomatous testicular germ cell tumors

After surgery and initial treatment, 126 patients with nonseminomatous germ cell tumors of the testis were followed by estimation of serum human chorionic gonadotropin (HCG), alpha-fetoprotein (AFP), and pregnancy-specific beta-1-glycoprotein (SP-1). The median follow-up time was 39 months (range, 12-69 months). An evaluation was made of the sensitivity, specificity, and predictive value of these markers to detect tumor relapse (TR) and partial remission (PR) rates. Five of the 35 (14%) Stage I patients had a TR, and in 4 the TR was recognized early by increasing serum levels of HCG (four times) and AFP (one time). In Stage II and III disease 17 of the 91 (18%) patients had a TR or PR. In 15 of the 17 patients TR and PR were associated with elevated serum levels of HCG (nine times), AFP (seven times), and SP-1 (five times). Rising levels of HCG and/or AFP preceded a clinical confirmation of TR and PR by 4 to 8 weeks. Serum SP-1 did not add useful information. The combined use of serum HCG and AFP gives a sensitive indicator for TR and PR: 19 of 22 (86%) of such patients were recognized. The specificity (98% and 100%, respectively) and the predictive value of positive tests (87% and 100%, respectively) were high for both HCG and AFP.

Suprapubic sonographic detection of prostate carcinoma.

Between January 1 and March 31, 1983, 103 patients scheduled for prostatic surgery were blindly evaluated preoperatively by suprapubic real time sonography. Prospectively, the sensitivity was 72.7%, specificity 72.2%, predictive value of positive test 51.6% and predictive value of negative 86.7% for the detection of prostatic carcinoma. Retrospective analysis increased the sensitivity to 86% and when clinical information was utilized, only one carcinoma escaped detection. Unfortunately, both prostatic inflammation and occasionally benign prostatic hypertrophy may simulate carcinoma sonographically, thus producing a significant number of false positives. No ultrasonically detectable characteristics could be found which unequivocally separate carcinomas from inflammation and hypertrophy. For this reason routine suprapubic screening does not seem warranted.

Increased concentrations of a transferrin variant after alcohol abuse

Isoelectric focusing in agarose gel has been used for separation of different molecular forms of transferrin (Tf) in sera and plasma from alcoholics and controls. One special form of transferrin with isoelectric point 5.7 (= Tf 5.7) was quantified by using zone immunoelectrophoresis assay (ZIA). This method was also used for quantification of total transferrin (Tf tot). Significant differences in the ratio Tf 5.7/Tf tot between the groups were obtained and the diagnostic sensitivities, specificities and predictive values of positive tests were 100, 97, 93.8%, respectively. Thus the results showed that this principle seems to be much better for detection of alcoholic abuse than currently used assays as γ-glutamyltransferase, etc. Samples taken on days following hospitalization showed that the Tf 5.7 7 values decreased over a two-week period of abstinence. Possible explanations for the abnormal quotient after ethanol abuse are discussed.

Carpal tunnel syndrome--course and prognosis.

In a retrospective study 157 patients with electrophysiologically proven carpal tunnel syndrome (CTS) were followed up. Of the 85 operatively treated patients, 86% showed clear improvement or cure, as did 32% of the patients not operated upon. Multivariate analysis of variance (MANOVA) and linear discriminant analyses indicated atrophy and length of history as effective predictors of clear improvement. The optimized discriminant point was ascertained in the receiver operator characteristics (ROC) curve. A predictive value of positive test of 0.89 was found for the course form "not cured" and a predictive value of negative test of 0.75 for the course form "cured" with a prevalence of one-third for the good course form. The prognosis was bad if atrophy occurred or the history exceeded 7 months. The determination of distal motor latency is indispensable for diagnosing CTS. For prognosis, however, length of history and clinical findings have been more helpful.

A comparison of three serological tests for the diagnosis of B. owis infection in rams.

The complement fixation test (CFT), the enzyme labelled immunosorbent assay (ELISA) and the gel diffusion precipitin test (GD) were compared, for the diagnosis of Brucellu ovis infection in rams. The sensitivities of the tests in 109 rams which were shedding B. ovis in their semen were: CFT 96.3%; ELISA 97.2%; GD 91.7%. The specificities of the tests in 141 rams from non-infected flocks were: CFI 99.3%; ELISA 98.6%; GD 100%. Predictive values of the three tests were measured in 285 rams from infected flocks. Thirty-eight percent of these rams were shedding B. ovis in their semen. Predictive values of positive tests were: CFT 75.5%; ELISA 66.7%; GD 72.5%. Predictive values of negative tests were: CFI 97.1%; ELISA 97.6%; GD 93.8%.