Prediction of the hepatitis C viremia using immunoassay data and clinical expertise.

Detection of anti-hepatitis C virus (anti-HCV) antibodies may yield a high frequency of false-positive results in people at low risk. To date, no clinical rule had been developed to predict viremia in HCV-seropositive patients. Therefore, we aimed to generate a prediction rule on the basis of clinical and serologic data, which can be used in outpatient care. We selected 114 seropositive patients without antiviral treatment or hepatitis B coinfection. Subsequently we identified independent predictors of the hepatitis C viremia by logistic regression and selected the quantitative value of the screening test for anti-HCV antibodies with the best performance in detecting viremia. Then, we combined clinical and serologic data to generate different prediction rules. Ratio of immunoassay signal strength of the sample to cut-off (S/CO) >15 had accuracy, positive predictive value (PPV) and positive likelihood ratio (LR+) of 84%, 83%, and 3.7; respectively. The rule compounded of the antecedent of blood transfusion before 1993 and S/CO >15 performed the best in prediction of viremia in all patients, with accuracy, PPV and LR+ of 71%, 88%, and 5.6; respectively. In the group of asymptomatic patients this rule improved in efficacy of prediction, with accuracy, PPV and LR+ of 79%, 91% and 12.8; respectively. In conclusion, a clinical rule is better than S/CO alone in prediction of the hepatitis C viremia. In a patient that meet the rule the probability of having viremia is high, therefore, it can be indicated directly an assay for viral load instead of other supplemental tests, thus, saving time and economic resources.