Correlation of Ziehl-Neelsen stain examination of sputum smear with cough time and chest X-ray radiographic features in cases with pulmonary tuberculosis

Objective To explore the correlation of Ziehl-Neelsen stain examination of sputum smear with cough time and chest X-ray radiographic features in patients with pulmonary tuberculosis, and to comprehend the risk factors of tuberculosis transmission. Methods The data from Guangzhou Tuberculosis Control Project New Cases Registration Book, including cough time, chest X-ray radiography, and Ziehl- Neelsen stain examination of sputum smear of new cases with pulmonary tuberculosis in the first outpatient department of our hospital from 2006 to 2015, were applied to analyzed the correlation of Ziehl-Neelsen stain examination of sputum smear with cough time and chest X-ray radiographic features by χ2 test. In the analysis, the cases were classified into five groups according to 4+、3+、2+、1+、- of Ziehl- Neelsen stain examination of sputum smear; according to the cough time, they were grouped into three kinds of duration——none, less than two weeks(< 2 weeks), and at least two weeks(≥ 2 weeks); the chest X-ray radiographic features included the presence and absence of cavity as well as the distribution of lesions in six lung fields (from one to six). Results 5 235 cases with pulmonary tuberculosis were enrolled; and the number of the five case groups from 4+ to - were 304, 213, 305, 973, and 3, 440, respectively. The analysis results were as follows. The overall percentages of the three kinds of duration were different or incompletely the same ( χ2=284.170, P =0.000) in the five case groups; the Cramer's V coefficient (for shortV) and corrected contingency coefficient(for shortr´) were 0.16 and 0.28, and there was a positive correlation between the positive level of sputum smear examination and cough duration. The overall percentages of those with or without cavity were different ( χ2=868.661, P=0.000); V and r´ were 0.41 and 0.53, and the positive level of sputum smear examination was closely related to the cavity. The overall percentages of the numbers of lung fields involved were different or incompletely the same ( χ2=524.543,P =0.000); V and r´ were 0.18 and 0.37, and there was a positive correlation between the positive level of sputum smear examination and the number of lung fields involved. Conclusions The positive level of sputum smear examination relates to cough duration, cavity, and the number of lung fields involved; and the correlation degree is from weak to strong according to this order.