Clinical application value of γ-IFN release assay combined with CA-125 in diagnosis of active pulmonary tuberculosis

Abstract

Objective: To evaluate the diagnosis of interferon gamma release assay (IGRA) combined with tumor marker carbohydrate antigen-125 (CA-125) in active pulmonary tuberculosis (PTB). Methods: One hundred and three patients with active PTB (48 definite and 55 clinical diagnosed), 646 patients with non-PTB pulmonary disease and 60 normal controls hospitalized in Beijing Tongren Hospital, Capital Medical University between January 2014 and December 2016 were retrospectively investigated. Blood samples were collected to determine the IGRA and CA-125 level by enzyme-linked immunosorbent assay and electrochemiluminescence, respectively. The CA-125 level of patients with active PTB, non-PTB pulmonary disease and normal controls were compared. Subsequently, the best cut-off value of CA-125 for diagnosing PTB was calculated based on 60 active PTB cases and 60 normal controls. Methodological evaluation of IGRA, CA-125 and combination of these two tests (both positive) for active PTB diagnosing were performed based on 43 active PTB cases and all the non-PTB pulmonary disease cases. Results: The median values of CA-125 among definite and clinical diagnosis groups of active PTB were 55.00 (25.35, 156.90) U/ml and 81.50 (39.40, 138.00) U/ml, respectively. There was no difference between the two groups (U=1 093.00, P>0.05). And the CA-125 level of male and female PTB patients were also undifferentiated (U=1 124.00, P>0.05). There were statistically significant differences in CA-125 levels between the active PTB group and all other non-PTB groups (all P<0.001), including those who had ever closely contacted with TB patients. The area under the ROC curve constructed by CA-125 for diagnosing active PTB was 0.933. And the best cut-off value of CA-125 was 22.00 U/ml. Based on this cut-off value, the accuracy, sensitivity and specificity of CA-125 for diagnosing active PTB were 70.5% (486/689), 86.0% (37/43) and 69.5% (449/646). The accuracy, sensitivity and specificity of IGRA for diagnosing active PTB were 73.3% (480/689), 90.7% (39/43) and 68.3%(441/64). The accuracy, sensitivity and specificity of IGRA combined with CA-125 for diagnosing active PTB were 90.6% (624/689), 76.7% (33/43), 91.5% (591/646). Both of the accuracy and the false positive ratio of this combinational method (8.5%, 55/646) were significantly lower than two indexes individually used (χ(2)=94.461, 88.261, P<0.001). However, the false negative ratio was increased to 23.3% (10/43) by combinational method. Conclusion: IGRA combined with CA-125 has a certain clinical value in diagnosis of active PTB, especially when the evidences of bacterial is not available.