Performance characteristics and clinical utility of a hybrid ELISA for detection of ANA

To investigate the clinical utility of a newly developed hybrid ELISA for a ntinuclear antibodies (ANA), a cross-sectional study of patients admitted t o the Section of Rheumatology was initiated. The ELISA was compared to indi rect immunofluorescence (IIF) on HEp-2 cells. Accuracy of tests was analyze d using receiver-operating characteristic methodology (ROC). In addition, d iagnostic sensitivity, specificity and predictive values were calculated fo r each assay. Results from the ROC analysis showed a slightly superior accu racy for IIF as compared to ELISA. Furthermore, IIF showed higher diagnosti c sensitivity and positive predictive value for all combinations of patient s and reference populations. This was due to enhanced detection by IIF, in contrast to ELISA, of diagnostically useful antibodies. IIF detected 87.4% and ELISA detected 84.2% of sera with antibodies against extractable nuclea r antigens (ENA). In addition, IIF detected diagnostically important antibo dies that are not included among the anti-ENA. The hybrid ELISA either lack s or does not contain the relevant antigens in sufficient amount. Inclusion of these antigens may further enhance the performance characteristics of t he ELISA.