Utility of T-cell interferon-γ release assays for the diagnosis of female genital tuberculosis in a tertiary referral hospital in Beijing, China

Diagnosis of female genital tuberculosis (FGTB) remains a challenge. The aim of this study was to evaluate the diagnostic value of T-SPOT.TB on peripheral blood mononuclear cells (PBMCs) for diagnosing FGTB in an area with high TB burden.Patients with suspected FGTB were enrolled consecutively between August 2010 and August 2015. T-SPOT.TB on PBMCs and histopathology were performed in all patients. T-SPOT.TB results were evaluated against patients' final diagnosis of FGTB which was made based on clinical manifestations, radiology, microbiological and histopathological evaluation, and response to anti-TB treatment. The sensitivity, specificity, predictive value, and likelihood ratio of T-SPOT.TB were analyzed.Among the 66 patients enrolled, 32 were diagnosed with confirmed FGTB, 33 with non-TB including ovarian tumor in 10 patients (30%), pelvic inflammatory diseases in 8 patients (24%), endometriosis in 7 patients (21%), endometrial polyps in 3 patients (9%), abscess of fallopian tube in 2 patients (6%), cyst of fallopian tube in 2 patients (6%), and endometrial carcinoma in 1 patient (3%). One patient with clinically indeterminate diagnosis was not included in the final analysis. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio, and negative likelihood ratio of T-SPOT.TB on PBMCs for diagnosis of FGTB were 94%, 70%, 75%, 92%, 3.09, and 0.09, respectively. Frequencies of spot forming cells (SFCs) of T-SPOT.TB were 430 (interquartile range [IQR] 155-706) SFCs/10 PBMCs and 124 (IQR 61-313) SFCs/10 PBMCs in FGTB and non-TB patients, respectively, and the difference was statistically significant (P = 2.14 × 10). By receiver operating characteristic curve analysis, a cutoff value of 40 SFCs/10 PBMCs of T-SPOT.TB had a sensitivity of 94% and specificity of 76% for the diagnosis of FGTB.T-SPOT.TB on PBMCs appeared to be a valuable and rapid diagnostic method for FGTB in TB endemic settings with high sensitivity and NPV.