Difference In Positive Predictive Value Research Articles

P-344: Diagnosis of stage I endometriosis: Comparing visual inspection to histologic biopsy

Endometriosis is frequently diagnosed by visual inspection however correlation of surgical impression with histology is variable, particularly in patients with stage I disease. Although pathology is the only way to definitively diagnose endometriosis, controversy exists as to whether biopsy is necessary to confirm the presence of disease. The objective of our study is to evaluate the positive predictive value (PPV) of surgical diagnosis compared to biopsy findings by severity of disease. Retrospective case series. Patients from an academic referral center who had laparoscopic biopsies for suspected endometriosis were included. In ten consecutive months 156 patients received diagnosis of endometriosis at laparoscopy. 104 of these patients had biopsies. The same surgeon performed all the surgeries. The location of the biopsies were recorded and sent to pathology for diagnosis. Revised ASRM endometriosis classification (1996) was used for staging. The pathologic diagnosis was then compared to the original stage of endometriosis at the time of surgery and the PPV was calculated. Chi-square analysis was done to evaluate biopsy accuracy by stage and location per biopsy and per patient. A total of 238 biopsies were taken from 104 patients. The ages of the patients ranged from 13-65 averaging 35.96 ± 7.58. The overall PPV was 87% for all patients. There were a total 73 suspected endometriomas removed and 165 peritoneal implants excised. The PPV per biopsy of stage I- IV endometriosis was 66%, 78%, 92% and 81% respectively (Table 1). The PPV per patient of stage I- IV endometriosis was 75%, 89%, 100%, and 90 % respectively (Table 2). Stages II-IV were significantly more likely to be confirmed by biopsy than stage I disease. When endometriomas and peritoneal biopsies were analyzed separately there was no difference in PPV (79% vs. 77%).Tabled 1Tabled 1 There was a high PPV for all patients in our study. However, when stage I endometriosis when compared to stages II-IV PPV was significantly lower. The PPV per patient was higher than the PPV per biopsy indicating that the ability to diagnose endometriosis may be improve by performing multiple biopsies. PPV of visual inspection is high, but not without errors. Therefore, in order to avoid misdiagnosis particularly in stage I disease, every attempt should be made to confirm diagnosis by biopsy.

P‐20 DIAGNOSTIC ACCURACY OF CONVENTIONAL SMEARS AND THINPREP SAMPLES IN CERVICAL SCREENING

Objective: Liquid Based Cytology has been recommended in England and Wales as the primary means of processing samples in cervical screening programme. We conducted this study to compare the positive predictive value (PPV) of conventional smears (CS) and ThinPrep samples (TP) reported as high‐grade squamous dyskaryosis and glandular neoplasia from September ’01 to August ’05. The performance of both techniques was compared with histological results.Methods: The database of the cytology department was searched and figures were obtained from September 2001 to August 2004 for high‐grade dyskaryosis and from September 2001 to August 2005 for glandular neoplasia. Only primary care samples were taken into consideration for determining positive predictive value (PPV).Results: The total number of samples for CS and TP were 373 990 (86.8%) and 48 216 (11.2%) respectively. Inadequate rate for CS and TP was 10.68% and 1.64% respectively. PPV of moderate and severe dyskaryosis including invasive carcinoma in CS was 71.7% and 90.4%; while for TP, it was 65.8% and 89.4% respectively. PPV of glandular neoplasia for CGIN/Adenocarcinoma was 66.7% and 64.3% in CS and TP respectively. PPV of glandular neoplasia for CIN2 and more in CS and TP was 82.7% and 85.7% respectively. The PPV for a diagnosis of CIN2 or worse in CS and TP was 79.3% and 73.3% respectively.Discussion: The PPV for a diagnosis of CIN2 or worse in both systems are within acceptable range for the U.K. (65–87%). The difference in PPV for varied categories in both systems is statistically insignificant. The inadequate rate is significantly reduced with TP.

P‐21 POSITIVE PREDICTIVE VALUE OF CERVICAL SMEARS REPORTED AS MILD DYSKARYOSIS

Objective: Recent national guidelines (NHSCSP Document 20) recommend the referral of patients having the first occurrence of mild dyskaryosis. We evaluated the usefulness of this guideline and determined the positive predictive value (PPV) of conventional smears (CS) and ThinPrep samples (TP) reported as the first occurrence of mild dyskaryosis.Methods: This was a retrospective study where we looked at the cases of mild dyskaryosis from January’05 to June’05 received at our laboratory. Of these, the cases of mild dyskaryosis at the first instance were only taken into consideration. Histological diagnosis of these cases where available were retrieved from the laboratory database and were correlated with the cytological findings.Results: There were 1016 cases, which were reported as mild dyskaryosis. Out of them, 51.1% (519 cases) were first report of mild dyskaryosis: 61.8% (321 cases) and 38.2% (198 cases) were CS and TP respectively. Of these, 181 CS (56.4%) and 120 TP (60.6%) had a histological follow up. The results showed that 54.1% CS and 56.7% TP had a low‐grade outcome, 26.0% CS and 25.8% TP had a high‐grade outcome and 19.9% CS and 17.5% TP had a normal outcome. The PPV of mild dyskaryosis for CIN1 or worse result was 53.0% and 50.0% in CS and TP respectively. The PPV of mild dyskaryosis for CIN1 only was 27.1% and 24.2% in CS and TP respectively.Discussion: The difference in PPV for both systems is statistically insignificant. This result endorses usefulness of colposcopic referral after the first report of mild dyskaryosis.

Hepatocellular Carcinoma in Patients with Chronic Liver Disease: Comparison of SPIO-enhanced MR Imaging and 16–Detector Row CT

To compare the sensitivity, positive predictive value, and diagnostic accuracy of superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance (MR) imaging with those of 16-detector row computed tomography (CT) for the detection of hepatocellular carcinoma (HCC) in patients with hepatitis B-induced cirrhosis. Institutional Review Board approval was obtained for this study, and informed consent was obtained from all patients. A total of 44 patients (36 men, eight women; age range, 35-67 years) with 59 HCCs and mild liver cirrhosis (Child-Pugh score A or B) underwent multiphasic CT and SPIO-enhanced MR imaging. The diagnosis of HCC was established at surgical resection (n = 31) and percutaneous biopsy (n = 28). SPIO-enhanced MR imaging was composed of T2-weighted turbo spin-echo and T2*-weighted gradient-echo sequences. Multiphasic CT consisted of four phases (ie, early arterial, late arterial, portal venous, and equilibrium). Three observers independently analyzed each image in random order. Sensitivity, positive predictive value, and diagnostic accuracy were calculated by using the alternative free-response receiver operating characteristic analysis for multi-detector row CT and SPIO-enhanced MR imaging. Although not significant (P > .05), the area under the receiver operating characteristic curve for SPIO-enhanced MR imaging (mean, 0.90) was higher than that for multi-detector row CT (mean, 0.82) for all observers. Also, although no significant difference was demonstrated by any of the three observers (P > .05), there was a trend toward increased sensitivity on both a per-lesion and a per-patient basis for SPIO-enhanced MR imaging (mean, 84.7% and 94.7%, respectively) compared with multi-detector row CT (mean, 76.9% and 88.6%, respectively). No significant difference in positive predictive value was observed between modalities. SPIO-enhanced MR imaging and multiphasic CT show similar diagnostic accuracy, sensitivity, and positive predictive value for the detection of HCC in patients with relatively mild hepatitis B-induced cirrhosis.

Selection of screening items for alcohol abuse and alcohol dependence among Mexicans and Mexican Americans in the emergency department.

This article reports on the selection of screening items to detect Mexican or Mexican-American patients in the emergency department (ED) who have alcohol problems and could benefit from an intervention or a referral for treatment. Items are tested against the Rapid Alcohol Problems Screen (RAPS), which has been optimized from standard screening instruments and has outperformed these instruments. The performance of individual items from standard screening instruments (CAGE, TWEAK, AUDIT, TRAUMA and BMAST) against International Classification of Diseases, Tenth Revision and Diagnostic and Statistical Manual, Fourth Revision criteria for alcohol abuse and dependence was evaluated in a merged probability sample (N = 869; 72% men) of 537 ED patients from three hospitals in Pachuca, Mexico, and 332 Mexican-American ED patients in Santa Clara County, CA. Logistic regression and tree-classification models were used for item selection. We found a prevalence of 15% for alcohol dependence and a prevalence of 28% for alcohol abuse or dependence in the merged sample. The RAPS items did not perform as well in terms of sensitivity (93%) as the optimal five items identified in these analyses (sensitivity = 98%) for alcohol dependence, but did demonstrate better specificity (79%) than the optimal five items (65%), which is an important consideration in a time of cost containment. Both sets of items showed better sensitivity and positive predictive value but similar Receiver Operating Characteristic values for respondents in the high acculturation group compared to those at other levels of acculturation. Differences in positive predictive value across all subgroups tended to increase at increased cutpoints, especially for the RAPS. These analyses suggest that the RAPS performs favorably compared to those items optimized, in this sample of Hispanic ED patients. Based on comparative item performance in these analyses, the RAPS may hold promise as a useful tool for screening for alcohol dependence, but requires further evaluation as a stand-alone instrument in comparison with other standard screening instruments.

Comparison of troponin T versus creatine kinase-MB in suspected acute coronary syndromes

Limitations of creatine kinase-MB (CK-MB) have led to alternative biochemical markers, including troponin T (TnT), to detect myocardial necrosis. Limited data are available regarding the predictive value of this new marker in patients with chest pain of uncertain etiology. Therefore, we prospectively compared CK-MB and TnT in a broad population with suspected acute coronary syndromes, including those admitted to a short-stay chest pain unit. CK-MB, quantitative TnT levels, and a rapid bedside assay were performed at 0, 4, 8, and 16 hours. Adverse events, including infarction, recurrent ischemia, coronary surgery, need for catheterization and/or intervention, stroke, congestive heart failure, or death, were identified by chart review and by follow-up phone call at 6 months. Of 707 patients, 104 were excluded for creatinine >2 mg/dl or incomplete data, leaving a total cohort of 603 patients. Coronary Care Unit admissions were 18%, intermediate care admissions were 14%, telemetry admissions is 21%, and admissions to 24-hour short-stay area were 47%. TnT (at 0.1 ng/ml) and CK-MB were positive in a similar proportion of patients (20.4% and 19.7%, respectively); however, the patients identified by TnT and CK-MB were not identical. In-hospital adverse events occurred in 37.1% with no differences in positive predictive value for the markers (p = NS). If CK-MB and TnT were negative, the early adverse event rate was 27%. No cardiac marker was positive by 16 hours in 54.9% of patients with an adverse event. Six-month follow-up was obtained in 576 of the 603 patients (95.5%). One hundred fifty-five late adverse events occurred in 134 patients (23.3%) at an average of 3.3 ± 2.5 months after discharge. If both markers were negative, the late event rate was 20.2% and did not increase in patients with positive CK-MB or TnT >0.2 ng/ml. However, the late event rate was substantially higher (52.9%) in those with intermediate TnT levels of 0.1 to 0.2 ng/ml (p = 0.002). Thus, TnT is a suitable alternative to CK-MB in patients with suspected acute coronary syndromes. The rapid bedside assay is comparable to quantitative TnT and may enable early diagnosis and triage. A negative cardiac marker value (TnT or CK-MB) does not necessarily confer a low risk of complication in patients presenting with acute chest pain to an emergency department.

Preoperative Pregnancy Testing in Ambulatory Surgery

Ian Lewis, M.B., B.S., M.R.C.P., F.R.C.A., Consultant in Anesthesiology.Jonathan Cooper, M.B., B.S., F.R.C.A., Senior Registrar in Anesthesiology, Shackleton Department of Anaesthetics, Level E, Center Block, Southampton University Hospital, Tremona Road, Southampton, SO 16 6YD, United Kingdom.To the Editor:--Manley et al. [1]found the true incidence of previously unrecognized pregnancy in menstruating women presenting for elective ambulatory surgery to be 7 of 2,056 (0.3%), as determined by urinary or serum human chorionic gonadotrophin immunoassay. Although this information is valuable, alone it is insufficient for the clinician to evaluate the significance of a positive or negative pregnancy test result in a single patient.The probability of pregnancy in a patient with a positive test result (positive predictive value) equals the number of true positives divided by the total number of positives (true positives + false positives); the probability of nonpregnancy in a patient with a negative test result (negative predictive value) equals the number of true negatives divided by the total number of negatives (true negatives + false negatives). The clinical significance of the pregnancy test is therefore given by the positive predictive and the negative predictive values. These values can be calculated from intrinsic properties of the test (sensitivity and specificity) and the estimated prevalence of pregnancy in the population in question. [2,3].Manley et al. [1]quote one false-positive pregnancy test among 179 adolescent women (0.6%) during preoperative testing from data by Malviya et al. [4]The specificity of the pregnancy test is therefore 178 of 179, 99.4%. Manley et al. [1]also state that the possibility of a false-negative result (pregnancy despite a negative test result) is "extremely remote." Let us assume, therefore, that the sensitivity of the test is 100% (a sensitivity of 99% would give virtually the same result in the following discussion).Consider a sample of 100,000 menstruating women presenting for elective ambulatory surgery. Given the original findings by Manley et al. [1]of a 0.3% pregnancy rate, there would be 300 pregnant and 99,700 nonpregnant women in the sample. Pregnancy testing of the 300 pregnant women would result in 300 true positives and no false negatives (100% sensitivity); pregnancy testing of the 99,700 nonpregnant women would result in 99,102 true negatives and 598 false positives (99.4% specificity). The positive predictive value is 300/300 + 598 = 33%, and the negative predictive value is 99,102/99,102 + 0 = 100%.Given that the aforementioned assumptions are valid, the clinician can be virtually 100% confident that a negative preoperative pregnancy test means that the patient is not pregnant. On the other hand, only 33% of women who test positive will be pregnant; the remaining 67% will have their surgery delayed but will not be pregnant. The latter statement is based on the specificity derived from data by Malviya et al. [4]Even if this assumption is not valid, when a population has a low overall prevalence of pregnancy (0.3% in this example), it is essential for the pregnancy test to be highly specific (few false positives) if a low positive predictive value is to be avoided. Improving the specificity to 99.95% (a false-positive rate of 1 in 2,000) would only result in an 86% positive predictive value given the same prevalence of pregnancy (0.3%).Although Manley et al. [1]and Malviya et al. [4]found what appear to be minor differences in specificity for preoperative pregnancy testing, the low prevalence of pregnancy in the population to be tested will result in large differences in positive predictive values. More data are required, preferably from large samples of women, before we can judge the clinical usefulness of preoperative pregnancy testing.Ian Lewis, M.B., B.S., M.R.C.P., F.R.C.A., Consultant in Anesthesiology.Jonathan Cooper, M.B., B.S., F.R.C.A., Senior Registrar in Anesthesiology, Shackleton Department of Anaesthetics, Level E, Center Block, Southampton University Hospital, Tremona Road, Southampton, SO 16 6YD, United Kingdom.