Comparison of detection values of acid-fast bacilli in sputum by direct smear versus liquid-based cytology smear

Objective To compare the detection values of direct smear and liquid-based cytology smear in the detection of acid-fast bacilli in sputum. Methods A total of 4 000 patients with tuberculosis admitted to Binzhou Central Hospital from May 2018 to May 2019 were selected. One sputum sample at night and one sputum sample at morning were collected from every patients. Finally, 8 000 specimens were enrolled in the study in total. Direct smear method and liquid-based cytology smear method were used to detect the 8 000 specimens. And the positive detection rates of acid-fast bacilli in sputum by two methods were recorded. Results The positive detection rates of acid-fast bacilli in the morning sputum sample by liquid-based cytology smear and direct smear were 30.33% (2 426/4 000) and 21.55% (1 724/4 000), respectively, and the positive detection rates of the night sputum samples by the two methods were 22.34% (1 787/4 000) and 12.40% (992/4 000) respectively. Compared with the night sputum samples, the positive detection rates of acid-fast bacilli in the morning sputum samples by two detection methods were higher, and the difference was statistically significant (P<0.05). Compared with direct smear method, the positive rates of acid-fast bacilli in the morning sputum samples and in the night sputum samples detected by liquid-based cytology smear method were higher, and the difference was statistically significant (P<0.05). Among the 8 000 specimens, the positive rates of salivary sputum, mucus sputum, blood sputum and purulent sputum detected by liquid-based cytology smear method were 14.52% (108/744), 12.09% (429/3 548), 65.49% (334/510) and 49.00% (1 567/3 198), respectively, And the positive detection rates of salivary sputum, mucus sputum, blood sputum and purulent sputum detected by direct smear method were 2.96% (22/744), 8.26% (293/3 548), 42.35% (216/510) and 36.34% (1 162/3 198), respectively. Compared with salivary sputum, mucus sputum and purulent sputum, the positive detection rates of acid-fast bacilli in blood sputum by the two methods were higher, and the difference was statistically significant (P<0.05). Compared with the direct smear method, the positive detection rates of sputum, mucus sputum, blood sputum and purulent sputum by liquid based cytology smear method were higher, and the difference was statistically significant (P<0.05). Conclusions The application of liquid-based cytology smear in the detection of acid-fast bacilli in sputum can effectively diagnose pulmonary tuberculosis and provide a basis for clinical diagnosis and treatment. Key words: Tuberculosis; Mycobacterium tuberculosis; Liquid-based cytology smear; Detection technology of acid-fast bacilli