Abstract:

Objective To analyze the influence of the quality of sputum samples collected from patients with newly diagnosed pulmonary tuberculosis on the results of bacteriological examinations, to provide a reference for clinical diagnosis and guidance on the importance of collecting good quality sputum samples.Methods A retrospective investigation was conducted on 564 sputum samples obtained from patients newly diagnosed with pulmonary tuberculosis at the Beijing Research Institute for Tuberculosis Control between January 2016 and December 2017. AFB smears and mycobacterium culture (including solid culture and liquid culture) were performed. The positive rate and positive grade of different qualities of sputum samples, and the positive rate obtained with different culture methods were analyzed using SPSS 17.0. Chi-square tests were used for comparing counting data. P<0.05 was considered statistically significant.Results Three sputum samples were collected for AFB examination per newly diagnosed tuberculosis case, and two sputum samples were simultaneously used for mycobacterial culture. A total of 1692 sputum samples were collected from 564 patients, 67.3% (1138/1692) of which passed quality grading. 242 cases (42.9%, 242/564) of pulmonary tuberculosis were confirmed. In 311 cases (55.1%, 311/564), all three sputum samples were of sufficient quality. Positive rates obtained for smears, solid culture, and liquid culture for sputum samples considered to be of sufficient quality were 21.1% (240/1138), 37.4% (258/690), and 68.0% (68/100), respectively, while that for sputum samples of poorer quality were 3.4% (19/554), 16.2% (49/302) and 27.8% (10/36), respectively. The differences in positive rates between sputum samples of good quality and those of poorer quality were statistically significant in all the tests used (χ ² values were 89.64, 44.04, and 17.51, respectively; Ps<0.001). Conclusion The rate of good quality sputum samples obtained from newly diagnosed pulmonary tuberculosis patients is relatively low. The rate of detection of Mycobacteria in good quality sputum samples is significantly higher than that in poorer quality sputum samples. It is thus very important to improve the quality of sputum samples collected.

Key words: Tuberculosis, pulmonary, Sputum, Specimen handling, Bacteriological techniques, Factor analysis, statistical, Outcome assessment (health care)