Development of a time-resolved fluoroimmunoassay of CFP-10 for rapid diagnosis of tuberculous pleural effusion

Tuberculous pleural effusion is the second most common form of extrapulmonary tuberculosis, which is very difficult to rapidly distinguish from malignant pleural effusion in the clinical setting. A time-resolved fluoroimmunoassay (TRF) of CFP-10, a low molecular weight protein secreted by pathogenic Mycobacterium tuberculosis, was developed to differentiate tuberculous pleural effusion from malignant one. The measuring range was 0.3-187.5 ng/ml with the dose-response coefficient of 0.9998 and detection limit of 0.036 ng/ml. The intra-assay and inter-assay coefficients of variation were 3.6-9.2% and 10.0-12.4%, respectively. The concentration of CFP-10 in malignant pleural effusion was less than 0.8 ng/ml. The negative predictive value was 93.1% in malignant pleural effusion (n = 247) while the positive predictive value was 83.0% in tuberculous pleural effusion (n = 235). Moreover, there was a statistically significant difference in the CFP-10 concentration of pleural effusion between the groups before and after clinical therapy of tuberculosis (P < 0.001, n = 81). In addition, the stability of the diagnostic reagents lasted at least 1 year at 4 °C. Therefore, the TRF of CFP-10 may be used for the rapid diagnosis of tuberculous pleural effusion and further monitoring the clinical therapeutic efficacy of tuberculosis.