Abstract:

Objective To explore the value of tuberculosis (TB) IgG antibody detection in assisting the diagnosis of tuberculosis.Methods The related clinical materials of 1494 inpatients and outpatients, who visited the Infectious Disease Hospital of Heilongjiang Province from July 2015 to May 2016, were collected. Among those patients, 1020 patients had pulmonary tuberculosis (PTB group), 54 patients had extra pulmonary TB (extra-PTB group) and 420 had other lung diseases excluding TB (other lung disease group). The clinical related materials of those patients were analyzed, including the results of TB IgG antibody detection, acid-fast bacillus smear microscopy, mycobacterium liquid culture, CT manifestations and clinical diagnosis.Results The sensitivity of TB IgG antibody detection in 1020 cases with PTB was 73.33% (748/1020) and there was statistically significant difference compared with the sensitivity of sputum smear (43.24%, 441/1020) and liquid culture (61.37%, 626/1020) (χ ²=190.02, P<0.001; χ ²=33.18, P<0.001). The sensitivity of TB IgG antibody detection in 54 cases with extra PTB was 62.96% (34/54) and there was statistically significant difference compared with the sensitivity of sputum smear (20.37%,11/54) and liquid culture (29.63%,16/54) (χ ²=20.15, P<0.001; χ ²=12.07, P=0.001). The sensitivity of TB IgG antibody detection had statistically significant difference (χ ²=553.47, P<0.001) between the PTB group and other lung disease group (6.90%, 29/420). The clinical diagnosis results was regarded as the diagnosis standard and a total of 1440 patients with PTB and other lung diseases were analyzed, the sensitivity, specificity and accuracy of TB IgG antibody detection were 73.33% (748/1020), 93.10% (391/420) and 79.10% (1139/1440), respectively. Among 1020 patients with PTB, the positive rate of TB IgG antibody detection was 86.85% (383/441) in the patients with smear-positive and 63.04% (365/579) in the patients with smear-negative, respectively (χ ²=72.56, P<0.001); the positive rate of TB IgG antibody detection was 80.51% (504/626) in the patients with liquid culture positive and 61.93% (244/394) in the patients with liquid culture negative (χ ²=42.70, P<0.001). The sputum smear and liquid culture results were regarded as the diagnosis standard and 1020 patients with PTB were analyzed, the sensitivity, specificity and accuracy of TB IgG antibody detection were 86.85% (383/441) and 80.51% (504/626), 36.96% (214/579) and 38.07% (150/394), 58.53% (597/1020) and 64.12% (654/1020). Among 1020 patients with PTB, 372 (36.47%) cases were smear negative and liquid culture negative. The positive rate of TB IgG antibody detection in 372 cases was 61.29% (228/372); In most of the patients (83.77%, 191/228) with positive for TB IgG antibody, their image findings by CT scan were “patch-like” or “strip-like”. The false positive rate of TB IgG antibody detection was 6.90% (29/420) in 420 patients with other lung diseases excluding TB and it mainly happened in the patients with pneumonia (62.07%, 18/29) and cancer (13.79%, 4/29). Conclusion TB IgG antibody detection plays a valuable role in assisting the diagnosis of tuberculosis, especially in smear and culture negative PTB and extra pulmonary tuberculosis.

Key words: Tuberculosis, Immunoglobulin G, Reagent kits, diagnostic, Comparative study, Data interpretation, statistical