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PubMed2000

Sensitivity, specificity and positive predictive value of patch testing: the more you test, the more you get? ESCD Working Party on Epidemiology.

Pathophysiological variability affects the results of patch testing. In addition, even a minimal degree of test-imprecision due to this variability has a number of important statistical consequences for the analysis and interpretation of any patch test data set. One such statistical phenomenon that is often overlooked is the dependence of the positive predictive value (i.e., the predictive value of a positive patch test) on sensitivity and specificity, the impact of which is heavily dependent on the proportion of truly allergic subjects that are studied. A 2nd important issue is the fact that patch testing is performed in series, which means multiple tests. If we assume, for example, a patch test series of only 10 allergens, then it can be demonstrated that there is a random probability of over 40%) to find, simply by chance, for at least 1 allergen, a statistically significant difference between 2 groups of patients. Comparison of the results of series between patients calls for statistical adjustments in order to prevent erroneously positive differences and/or associations.

Dermatitis, Allergic Contact↗
PubMed1998

Utilization and predictive value of laboratory tests in patients referred to rheumatologists by primary care physicians.

OBJECTIVE: Antinuclear antibodies (ANA), rheumatoid factors (RF), and erythrocyte sedimentation rate (ESR) are among the most frequently requested tests in the diagnosis and investigation of connective tissue diseases (CTD). We evaluate the utilization patterns and predictive value of these tests in patients referred to rheumatologists by primary care physicians. METHODS: We reviewed the records of all new patients referred by primary care physicians in 1994 to 2 rheumatologists practicing at the University of Alberta. Data extracted from the records included diagnostic tests requested by referring primary care physicians, signs and symptoms at the initial rheumatology consult, and followup diagnoses. RESULTS: Seven hundred eleven new patients had been referred by over 300 primary care physicians: RF had been requested in 25%, ANA in 21%, and ESR in 29%. One hundred nine (15%) of the 711 patients had a CTD, 45 (6%) had rheumatoid arthritis (RA), and 8 (1%) systemic lupus erythematosus (SLE). The predictive values of positive tests for the diagnosis of CTD were low: 49% for RF, 29% for ANA, and 35% for ESR. For RA, the positive predictive values were 44% for RF, 8% for ANA, 17% for ESR; for SLE, 2, 12, and 3%, respectively. Diffuse musculoskeletal pain and fatigue were significantly associated with test utilization, although most patients with these symptoms had fibromyalgia or localized soft tissue rheumatism. CONCLUSION: Primary care physicians frequently requested autoantibodies in patients referred to rheumatologists. Most tests were negative, and were often requested in patients without CTD, resulting in low positive predictive values and questionable clinical utility. These findings suggest inappropriate overuse and lack of understanding of the use of autoantibody tests in diagnosing rheumatic diseases. A decrease in inappropriate use could be achieved by emphasizing that fatigue and diffuse musculoskeletal pain are not indicative of CTD in the absence of other features such as joint swelling, typical rash, or organ involvement.

Adult↗
PubMed2005

Limited predictive value of an acute test with subcutaneous octreotide for long-term IGF-I normalization with Sandostatin LAR in acromegaly.

OBJECTIVES: To study whether the growth hormone (GH) response after the subcutaneous administration 50 microg of octreotide (acute octreotide test) has any predictive value for long-term IGF-I normalization with Sandostatin LAR. DESIGN: Twenty four therapy-naive patients with active acromegaly were studied. RESULTS: > 75% GH decrease in the acute octreotide test predicted long-term IGF-I normalization with Sandostatin LAR in 8/11 (73%) of patients. 3/13 (23%) patients with < 75% GH decrease in the acute octreotide test were long-term biochemically controlled with Sandostatin LAR. Using the > 75% GH reduction criterion, the sensitivity and specificity of this test for predicting long-term normalization of serum IGF-I with Sandostatin LAR treatment were 73% and 77%, respectively (positive and negative predictive values: 73% and 77%, respectively). 6/8 (75%) patients with GH suppression to levels < 1.1 microg/l and 9/16 (56%) patients with GH suppression to levels < 2 microg/l in the acute octreotide test showed normalization of serum IGF-I with long-term Sandostatin LAR treatment. The sensitivity and specificity of GH suppression < 1.1 microg/l for predicting of the long-term normalization of serum IGF-I with Sandostatin LAR therapy were 55% and 85%, respectively (positive and negative predictive values: 75% and 69%, respectively). The sensitivity and specificity of GH suppression < 2 microg/l for predicting of the long-term normalization of serum IGF-I with Sandostatin LAR therapy were 82% and 46%, respectively (positive and negative predictive values: 56% and 75%, respectively). CONCLUSION: The acute octreotide is not recommended for clinical decision making with regard to long-term treatment using the long-acting somatostatin analog Sandostatin LAR in acromegaly.

Acromegaly↗
PubMed1984

The prevalence, six-month persistence, and predictive values of laboratory indicators of bacterial vaginosis (nonspecific vaginitis) in asymptomatic women.

The natural course of signs and laboratory test findings indicative of bacterial vaginosis was followed in an observational noninterventive 6-month longitudinal study of 270 asymptomatic women. Only the minority of positive Gardnerella vaginalis cultures (5 of 33), wet mount clue cells (5 of 14), sniff tests (3 of 11), Papanicolaou smear clue cells (0 of 5), and discharge consistent with bacterial vaginosis (11 of 49) persisted in the absence of therapy. While these four laboratory parameters as well as chromatographic succinate/lactate ratios (performed only on the final visit) were abnormal significantly more often in patients with abnormal discharge than in those with normal discharge (p = 0.006, p less than 0.0001, p less than 0.0001, p = 0.0003, and p = 0.002, respectively), all were insensitive predictors of abnormal discharge with sensitivities ranging between 10.6% and 20.2% and abnormal test predictive values between 30.6% and 65.2%. We conclude that G. vaginalis represents indigenous flora in some normal women and that therapy is unwarranted for the incidental finding of a positive laboratory indicator of bacterial vaginosis in the patient without symptoms.

Adolescent↗
PubMed2005

Use of simulation modeling to estimate herd-level sensitivity, specificity, and predictive values of diagnostic tests for detection of tuberculosis in cattle.

OBJECTIVE: To estimate herd-level sensitivity (HSe), specificity (HSp), and predictive values for a positive (HPVP) and negative (HPVN) test result for several testing scenarios for detection of tuberculosis in cattle by use of simulation modeling. SAMPLE POPULATION: Empirical distributions of all herds (15,468) and herds in a 10-county area (1,016) in Michigan. PROCEDURE: 5 test scenarios were simulated: scenario 1, serial interpretation of the caudal fold tuberculin (CFT) test and comparative cervical test (CCT); scenario 2, serial interpretation of the CFT test and CCT, microbial culture for mycobacteria, and polymerase chain reaction assay; scenario 3, same as scenario 2 but specificity was fixed at 1.0; and scenario 4, sensitivity was 0.9 (scenario 4a) or 0.95 (scenario 4b), and specificity was fixed at 1.0. RESULTS: Estimates for HSe were reasonably high, ranging between 0.712 and 0.840. Estimates for HSp were low when specificity was not fixed at 1.0. Estimates of HPVP were low for scenarios 1 and 2 (0.042 and 0.143, respectively) but increased to 1.0 when specificity was fixed at 1.0. The HPVN remained high for all 5 scenarios, ranging between 0.995 and 0.997. As herd size increased, HSe increased and HSp and HPVP decreased. However, fixing specificity at 1.0 had only minor effects on HSp and HPVN, but HSe was low when the herd size was small. CONCLUSIONS AND CLINICAL RELEVANCE: Tests used for detecting cattle herds infected with tuberculosis work well on a herd basis. Herds with < approximately 100 cattle should be tested more frequently or for a longer duration than larger herds to ensure that these small herds are free of tuberculosis.

Animals↗
PubMed2005

The predictive value of the extensor grip test for the effectiveness of bracing for tennis elbow.

BACKGROUND: Tennis elbow is a common complaint. Several treatment strategies, such as corticosteroid injections and physical therapy and braces, have been described. HYPOTHESIS: The extensor grip test has predictive value in assessing the effectiveness of bracing in tennis elbow. STUDY DESIGN: Cohort study (prognosis); Level of evidence, 1. METHODS: Patients with tennis elbow complaints were randomized into 3 groups: brace only, physical therapy, and combination brace and physical therapy. The extensor grip test was performed before randomization on all patients. Outcome measures at 6-week follow-up were success rate, severity of complaints, pain, disability, inconvenience during daily life, and satisfaction. RESULTS: In the brace-only group, significant differences were identified between patients with a positive test result and patients with a negative test result for 3 outcome measures. The success rate in the test-negative group was 23% (5/22) compared to 47% (21/45) in the test-positive group. Mean decrease in pain was 23 (95% confidence interval, -3 to 49) in the test-positive group compared to 11 (95% confidence interval, -6 to 28) in the test-negative group, and mean satisfaction in the test-positive group was 71 (95% confidence interval, 48 to 94) compared to 51 (95% confidence interval, 24 to 78) in the test-negative group. In the physical therapy and combination groups, no differences were identified between test-positive and test-negative patients. CONCLUSION: The extensor grip test seems valuable as a predictive factor for the effectiveness of bracing as treatment for tennis elbow over the short term.

Adult↗
PubMed1999

Predictive value of the intracarotid amobarbital test in bihemispheric seizure onset.

The intracarotid amobarbital test (IAT) is used to lateralize language function and assess hemispheric memory. In this study 23 non-lesional epileptic patients were evaluated. The magnitude of the difference in IAT scores between the two hemispheres was significantly greater in the patients whose seizures lateralized on scalp or intracranial EEG than in patients with bihemispheric seizure onset. This suggests that the IAT is useful not only in predicting lateralized seizure focus, but bihemispheric onset as well.

Adult↗
PubMedDate not supplied

Cariogenic oral flora and its relation to dental caries.

Many attempts have been made to establish the risk profile of dental caries; however, no diagnostic procedures are yet available to reliably predict such risk particularly among the pediatric and adolescent population. Age of subject, a history of caries affecting the primary dentition, the prevalence of Streptococcus mutans, pH values, salivary flow, and the frequency and amount of sugar consumption have been the factors most studied. A cross-sectional study is made of schoolchildren in the 12-13-year age-range to evaluate the relationship between dental caries and CFU/ml of S. mutans and Lactobacillus, salivary buffer capacity, and salivary flow. Likewise, an evaluation is made of the predictive value of the variables, bacterial count and salivary pH with respect to caries. A total of 167 children were subjected to oral examination to establish the DMFT and DMFS indices, followed by the collection of saliva for quantitating S. mutans, Lactobacillus, pH and salivary flow, by the Dentocult (SM)(LB) and Dentobuff systems (Vivadent). The data obtained were subjected to descriptive analysis, comparisons among variables were made by nonparametric testing with a confidence level of 95 percent. Test predictive value was studied in terms of sensitivity, specificity, positive and negative predictive values, and probability ratio. Statistically significant (p < 0.001) correlations were observed between the caries indices and bacterial counts. No significant association was recorded with the rest of the variables studied. Bacterial counts as well as salivary buffer capacities exhibited greater negative than positive predictive values, i.e., they were more effective in identifying healthy individuals than patients who required treatment.

Adolescent↗
PubMed1986

[What does neutropenia tell about the existence of sepsis in the newborn? Predictive value of clinical laboratory tests].

A laboratory test can have one of three different functions. As a confirmatory test it can prove a diagnosis, as a screening test it can indicate the probability, that a disease in question is actually present, and as a monitoring test it can be used to guide a medical therapy. To assess the clinical value of a screening test the criteria of sensitivity, specificity and predictive value are commonly used. The meaning of these terms is explained using the example of neutropenia as a screening test for sepsis on the first day of life. For the neonates admitted during their first day of life to the neonatology units of the obstetric and paediatric departments of Zurich University a neutrophil count below 3 X 10(9)/1 as a test for sepsis has a sensitivity of 67%, a specificity of 96.7%, a predictive value of the positive test of 20%, and a predictive value of the negative test of 99.6%. The predictive value of a test is strongly dependent on the prevalence of the disease looked for in the population under study. Variation of the cut off point of a screening test results in a change of its sensitivity and predictive value of the positive test in the opposite direction.

Age Factors↗
PubMed1986

Thrombosis, recurrent fetal loss, and thrombocytopenia. Predictive value of the anticardiolipin antibody test.

To determine the predictive value of the IgG anticardiolipin antibody (ACA) test for thrombosis, recurrent fetal loss, and thrombocytopenia, the clinical features of 121 patients with varying antibody levels were studied. When patients were grouped into high-positive, low-positive, and normal groups according to their ACA levels, there were strong statistical correlations with arterial thrombosis, venous thrombosis, fetal loss, thrombocytopenia, and a positive Coombs' test. At levels of 7 SD and above, the test was highly specific (greater than 80%) and predictive (greater than 70%) for thrombosis, thrombocytopenia, and recurrent fetal loss. This study suggests that the IgG ACA test may be a useful predictor for thrombosis, recurrent fetal loss, and thrombocytopenia in patients with autoimmune disorders.

Abortion, Habitual↗
PubMed1994

The predictive value of diagnostic tests for pheochromocytoma.

BACKGROUND: Ascertaining or excluding a pheochromocytoma may be difficult. The purpose of this study is to identify preoperative tests that are good predictors of a pheochromocytoma. METHODS: Patients presumptively diagnosed with a pheochromocytoma based on clinical assessment, plasma or urinary catecholamines, computed tomography, or magnetic resonance imaging were analyzed. The sensitivity, specificity, positive, and negative predictive values were determined for each test based on the pathologic finding of a pheochromocytoma. Data were analyzed with Student's t test or Fisher's exact test. RESULTS: Of 14 patients, seven had pathologically proven pheochromocytomas, whereas three had cortical adenomas. In four patients, a pheochromocytoma was excluded by repeat testing. The 24-hour urinary mean metanephrine levels were significantly different between patients with and without pheochromocytomas (5.8 micrograms vs 0.5 micrograms, p = 0.05) and had the best positive predictive value (83%) and negative predictive value (100%) of the biochemical tests. T2-weighted magnetic resonance imaging had a 100% positive and negative predictive value. Age, sex, symptoms, blood pressure, tumor location, tumor size, and plasma catecholamine levels could not accurately predict or exclude a pheochromocytoma. CONCLUSIONS: T2-weighted magnetic resonance imaging is the imaging study of choice for predicting a pheochromocytoma. The 24-hour urinary metanephrine level is the single best biochemical indicator of a pheochromocytoma. Plasma catecholamine levels and computed tomography are not helpful in diagnosing or excluding a pheochromocytoma.

Adrenal Gland Neoplasms↗
PubMedDate not supplied

Predictive value of coagulation tests in arterial thrombosis.

In five large-scale prospective studies the predictive value of hemostatic parameters indicating the occurrence of arterial thrombotic diseases has been estimated in healthy individuals. All the studies have consistently found a statistically significant association between hyperfibrinogenemia and arterial thrombotic diseases. In two studies, increased levels of factor VII were associated with an increased incidence of ischemic heart disease. The relationship between arterial occlusive diseases and plasma levels of fibrinogen or factor VII was closer than that for other well established risk factors such as plasma cholesterol. These data indicate the important pathogenetic role carried out by alterations of the clotting system in occlusive arterial diseases.

Adult↗
PubMed1994

Predictive validity of the Braden Scale for pressure sore risk in a nursing home population.

The predictive validity of the Braden Scale and the timing of assessment for optimal prediction of pressure sore development (PS) were studied in a nursing home population. Subjects (N = 102) over age 19, free of PS and admitted within the previous 72 hr, were randomly selected from consecutive admissions to a skilled nursing facility. Subjects were assessed for risk and skin condition every 48 to 72 hr for 4 weeks. Twenty-eight subjects (27.5%) developed a PS. A cut score of 18 used at the observation prior to the first recorded PS maximized prediction, producing a sensitivity of 79%, a specificity of 74%, a 54% predictive value of a positive test, 90% predictive value of a negative test, and 75% correct classification rate.

Aged↗
PubMed2001

Predictive value of latex agglutination test in serological screening for Toxoplasma gondii.

The predictive value of commercial latex agglutination kit (Toxo-Screen DA, bioMerieux) was assessed for use as screening test for Toxoplasma IgG antibody. The sensivity and specificity were also compared with those of the reference standard Sabin-Feldman dye test. Five hundred serum samples were collected from 200 blood donors and 100 each from pregnant women, kidney recipients and HIV infected persons. Eighty (16.0%) out of 500 subjects were positive for Toxoplama IgG antibody by Toxo-Screen DA (bioMerieux) compared with 57 (11.4%) by Sabin-Feldman dye test. The sensivity and specificity of Toxo-Screen DA (bioMerieux) were 100% and 94.8 % respectively which were similar to previous reports from the area of high prevalence of Toxoplasma infection. In present study the positive predictive value of Toxo-Screen DA (bioMerieux) was only 71.3%. The latex agglutination test should be considered as a screening test for Toxoplasma antibody, especially by small laboratories in remote area due to its availability, simplicity, sensitivity and specificity. However, because of its moderate positive predictive value, the test should be used with caution in screening immunocompromised patients and pregnant women living in areas with low prevalence of Toxoplasma infection. Since the number of false seropositive cases would be relatively higher than in a highly prevalent area, confirmation by the dye test would be needed.

Adolescent↗
PubMed2005

Annual conversion to alzheimer disease among patients with memory complaints attending an outpatient memory clinic: the influence of amnestic mild cognitive impairment and the predictive value of neuropsychological testing.

OBJECTIVE: The goals of this study were to determine the annual conversion rate to Alzheimer disease (AD) among patients reporting memory problems, including a subgroup with amnestic mild cognitive impairment (aMCI), and to investigate the predictive value of neurocognitive testing for future dementia. METHODS: A prospective study was carried out in an outpatient memory clinic. One hundred and seven patients underwent a clinical examination and completed a battery of standard cognitive tests at study entry and two years later. The conversion rate to clinically manifested AD two years later was investigated and sensitivity, specificity, receiver operating characteristics (AUC), positive predictive value and negative predictive value for each neuropsychological test were determined. RESULTS: We found an annual rate of conversion to AD of 6.5% among patients reporting memory decline in the setting of our clinic. Specifically, patients with aMCI had an annual conversion rate of approximately 20%. The annual conversion rate for patients reporting memory problems but showing no memory deficit at memory testing was approximately 3%. Receiver operating characteristics (AUC) of the neuropsychological tests ranged from 0.60 to 0.94. CONCLUSIONS: Patients with aMCI have 8.6-fold higher odds of developing AD compared with patients without evident memory impairment on neuropsychological testing. Although the risk of developing AD among patients without objective memory decline is small, some patients in this group still convert to AD and therefore close clinical monitoring of patients is necessary.

Aged↗