BACKGROUND: The prostate-specific antigen (PSA) is considered the most useful among tumor markers currently used. However, its quantitative results are interpreted only qualitatively for the diagnosis of prostate cancer. The recently introduced information theory enables the information of the quantitative results transformed into Shannon's entropy (S) that represents uncertainties and then "1-S" representing diagnostic certainty. METHODS: The 882 urological patients enrolled were categorized into 2 groups: a patient group comprising 233 patients with prostate cancer and a disease control group comprising 649 patients with benign prostate disease. The level of PSA in all the patients was tested and was found to be > or =2 ng/mL. The variables like PSA level and age were modeled on logistic regression analysis to predict the probability of prostate cancer and the diagnostic certainty. RESULTS: The mean (SD) of PSA levels in the patient group and the disease control group were 44.5 ng/mL (37.62 ng/mL) and 5.7 ng/mL (3.70 ng/mL), respectively. The logistic regression model fitted well when the age variable was dichotomized at the age of 55 yr. The diagnostic certainty was lowest at a PSA level of 18.90 ng/mL in the <55-yr age group, and 15.45 ng/mL in the >55-yr age group. CONCLUSIONS: The diagnostic certainty (1-S) of whether to diagnose prostate cancer or not at a certain PSA level could be obtained using the information theory. The methodology used in this study may help interpret the results of other quantitative tests.
Age Factors ; Aged ; Entropy ; Humans ; *Information Theory ; Logistic Models ; Male ; Middle Aged ; Prostate-Specific Antigen/*blood ; Prostatic Diseases/diagnosis ; Prostatic Neoplasms/*diagnosis

BACKGROUND: Many studies evaluating the performance of in vitro diagnostic kits have been criticized for the lack of reliability. To attain reliability those evaluation studies should be preceded by sample size calculation ensuring statistical power. This study was intended to develop a web-based system to estimate the sample size, which was often neglected because it would require expert knowledge in statistics. METHODS: For sample size calculation, we extracted essential parameters from the performance studies on the 3rd generation anti-hepatitis C virus (HCV) kits reported in the literature. We developed a system with PHP web-script language and MySQL. The statistical models used in this system were as follows; one sample without power consideration (model 1), one sample with power consideration (model 2), and two samples with power consideration (model 3). RESULTS: Among the articles published between 1989 and 2005, 13 articles that evaluated the performance of anti-HCV kits were identified by searching with Medical Subject Headings (MeSH). The diagnostic sensitivity was 83-100% with a median of 145 samples (range; 12-1,091) and the specificity was 97-100% with a median of 1,025 samples (range; 33-4,381). The estimated sample size would be 280 in the model 1, 817 in the model 2, and 1,510 in the model 3, when we set 2% prevalence of HCV infection, 95% sensitivity of a conventional kit, 97% sensitivity of a new kit , 95% significance level (two-sided test), 2% allowable error, and 80% power. CONCLUSIONS: Our study indicates that an insufficient sample size is still a problem in performance evaluation. Our system should be helpful in increasing the reliability of performance evaluation by providing an appropriate sample size.
Medical Subject Headings ; Models, Statistical ; Prevalence ; Sample Size* ; Sensitivity and Specificity

PURPOSE: We wanted to determine the differential points between craniopharyngioma and pituitary macroadenoma on MRI. MATERIALS AND METHODS: The MRI findings in twenty seven patients (age range: 14-67 years, mean age: 46 years, 17 males and 10 females) with pathologically proven craniopharyngioma and twenty four patients (age range: 23-64 years, mean age: 54 years, 8 males and 16 females) with pathologically proven pituitary macroadenoma were analyzed retrospectively by two radiologists. We analyzed the location, the contour of the mass, the presence of high signal intensity on the T1 weighted images, the thickness of the enhancing wall, separation between the mass and the pituitary gland, and the presence of attachment or compression to the midbrain. RESULTS: On MRI, craniopharyngiomas showed a suprasellar location, high signal intensity on the T1 weighted images and a larger suprasellar portion. After contrast enhancement, the separation of the mass from the pituitary gland is more distinct than that of the pituitary macroadenomas. The craniopharyngiomas showed the presence of attachment or compression to the midbrain. The pituitary macroadenomas had a larger intra- or infrasellar portion than that of the craniopharyngiomas, and they also showed a thicker enhancing wall after contrast enhancement. CONCLUSION: The location, contour of the mass, presence of high signal intensity on T1 weighted images, thickness of the enhancing wall, separation of the mass from the pituitary gland and the presence of attachment or compression to midbrain are useful differential points between craniophayngioma and pituitary macroadenoma on MRI.
Craniopharyngioma* ; Humans ; Magnetic Resonance Imaging ; Male ; Mesencephalon ; Pituitary Gland ; Retrospective Studies

PURPOSE: To intra-individually compare diagnostic accuracy of high-resolution contrast-enhanced magnetic resonance angiography (CE-MRA) with computed tomography angiography (CTA) and digital subtraction angiography (DSA) for the assessment of supraaortic steno-occlusive disease. MATERIALS AND METHODS: Twenty-eight patients (20 men, 8 women, 53-79 years of age) underwent supraaortic CE-MRA, CTA and DSA. CE-MRA was performed on two 1.5T MR scanners (voxel dimension: 0.66x0.66x1.1 or 1.2 mm3), and CTA on 64-slice CT scanners (voxel dimension: 0.42x0.42x0.63 mm3). All the three examinations were completed within 40 days (median 19 days; range 1-40 days). Retrospective evaluation and measurement of diameter of 6 extracranial and 9 intracranial arterial segments was done by 2 experienced radiologists. RESULTS: A total of 420 arterial segments were examined by CE-MRA, CTA and DSA. On DSA, 34 stenoocclusive lesions were noted at extracranial (n=19) and intracranial (n=15) vessels. For extracranial stenosis greater than 70%, sensitivity, specificity, positive predictive value (PPV) and negative predictive values (NPV) were 94.7%, 98.7%, 90.0% and 99.3% on CE-MRA, and 94.7%, 99.3%, 94.7% and 99.3% on CTA. For intracranial stenosis greater than 50%, sensitivity, specificity, PPV and NPV were 93.3%, 98.3%, 77.8%and 99.6% on CE-MRA, and 86.7%, 97.9%, 72.2% and 99.1% on CTA, with DSA as the standard of reference. CONCLUSION: Supraaortic CE-MRA is as reliable as CTA in depicting the arterial stenosis, and is effective in screening of significant stenosis of both extracranial and intracranial arterial stenosis.
Angiography ; Angiography, Digital Subtraction ; Constriction, Pathologic ; Female ; Humans ; Magnetic Resonance Angiography ; Magnetic Resonance Spectroscopy ; Magnetics ; Magnets ; Male ; Mass Screening ; Retrospective Studies ; Sensitivity and Specificity

BACKGROUND: The third generation anti-hepatitis C virus (HCV) enzyme immunoassay (EIA) is now in use for screening HCV infection. The aim of this study was to pool the data on the sensitivity and specificity of third generation anti-HCV EIA tests after evaluating the quality of the studies using Standards for Reporting of Diagnostic Accuracy studies (STARD) checklist. METHODS: We searched MEDLINE and PubMed databases using keywords about the accuracy of diagnostic tests for HCV infections. Methodological quality was assessed by two persons with a modified STARD checklist. A heterogeneity test was performed, and in case heterogeneity was present, a sub-group analysis was done. Fixed-effects model was used to obtain pool sensitivity and specificity with 95% confidence intervals (CI). RESULTS: A total of 41 studies from 16 papers were selected. The quality score ranged from 6 to 13 (median 10.5); Inter-observer agreement was 93.62% (k=0.69); and 41 studies revealed heterogeneity. We performed a sub-group analysis with only 28 studies from 13 papers that were evaluated to be of high quality. A subgroup using polymerase chain reaction as the reference test revealed homogeneity and was calculated the pooled sensitivity and specificity of 99.92% (CI 99.77-100.07%) and 99.66% (CI 99.45-99.86%) respectively. Studies on test kits with an increased reactivity to the core region also showed homogeneity in sensitivity and the pooled sensitivity was 99.78% (CI 99.53-100.03%). CONCLUSIONS: For the first time in Korea, the diagnostic accuracy of test kits was evaluated by meta-analysis using STARD checklist. The methodology shown in this study should help extending laboratory medicine to an evidence-based medicine.
Checklist* ; Diagnostic Tests, Routine* ; Evidence-Based Medicine ; Humans ; Immunoenzyme Techniques ; Korea ; Mass Screening ; Polymerase Chain Reaction ; Population Characteristics ; Sensitivity and Specificity*

The aims of this study were to summarize results on the association of HLA-DRB1 with rheumatoid arthritis (RA) in Asians and to determine if the shared epitope (SE) hypothesis could explain the meta-analysis results. Among the papers published between January 1987 and July 2006 on RA susceptibility in Asian-Mongoloid populations (Korean, Japanese, Chinese, and Thai), 12 were selected for the metaanalysis. Mongoloid-Asian patients with RA had significantly higher frequencies of HLA-DRB1*0101, *0401, *0410, and *1001 than controls (OR 1.5-2.1, p<0.05 for association). When analyses were restricted to more ethnically homogeneous populations, HLA-DRB1*0405 showed a significant susceptibility to RA in Koreans (OR 5.65, 95% CI 4.32-7.39), whereas the HLA-DRB1*0301, *0403, *0406, *0701, *1301, and *1405 alleles showed protective association with RA (OR 0.32-0.70, p<0.05 for association). In conclusion, it was found that HLA-DRB1 *0101, *0401, *0405, *0410, and *1001 are susceptible, while HLA-DRB1* 0301, *0403, *0406, *0701, *1301, and *1405 are protective in Asian-Mongoloids. All the RA-associated alleles except DRB1*0301 could be explained by the structural model supporting the SE hypothesis that RA susceptibility is determined by the combination of amino acid residues at HLA-DR beta71 and beta74, not by beta71 alone.
*Alleles ; Arthritis, Rheumatoid/*genetics ; Asian Continental Ancestry Group/*genetics ; *Genetic Predisposition to Disease ; HLA-DR Antigens/chemistry/*genetics ; Humans