Table 4. The association of QFT positivity and smoking status by age, gender and TB contact history among total study populations.

Variables&		QFT positivity (n/N)	%	Adjusted OR (95%CI)
Gender and smoking status†
Female	Never-smoker	1791/10732	16.69	Reference
	Ever-smoker	41/131	31.30	1.70 (1.16, 2.50)
Male	Never-smoker	695/4584	15.16	Reference
	Ever-smoker	1427/4961	28.76	1.45 (1.30, 1.61)
p for likelihood ratio test				0.842
Age and smoking status‡
5–19 years	Never-smoker	96/3439	2.79	Reference
	Ever-smoker	4/46	8.70	3.44 (1.16, 10.16)
20–39 years	Never-smoker	322/3027	10.64	Reference
	Ever-smoker	166/1096	15.15	1.40 (1.07, 1.85)
40–59 years	Never-smoker	1112/5564	19.99	Reference
	Ever-smoker	698/2424	28.80	1.32 (1.13, 1.55)
≥ 60 years	Never-smoker	956/3286	29.09	Reference
	Ever-smoker	600/1526	39.32	1.31 (1.10,1.55)
p for likelihood ratio test				0.002
TB contact history and smoking status#
No	Never-smoker	2341/14756	15.86	Reference
	Ever-smoker	1381/4862	28.40	1.49 (1.34, 1.66)
Yes	Never-smoker	144/553	26.04	Reference
	Ever-smoker	87/228	38.16	1.32 (0.84, 2.06)
p for likelihood ratio test				0.931
BMI and smoking status*
<28.0(kg/m2)	Never-smoker	2168/13853	15.65	Reference
	Ever-smoker	1321/4557	28.99	1.47 (1.32, 1.97)
≥28.0 (kg/m2)	Never-smoker	318/1463	21.74	Reference
	Ever-smoker	147/535	27.48	1.55 (1.11, 2.15)
p for likelihood ratio test				0.838

Abbreviations: BMI = Body mass index; CI = confidence interval; OR = odds ratio; QFT = QuantiFERON-TB Gold In-Tube; TB = tuberculosis. Participants with indeterminate results were not included in this analysis. Sum might not always be in total because of missing data.

^& Variables independently associated with QFT positivity identified in Table 2 were considered in this analysis.

^†Adjusted for age, BMI and TB contact history.

^‡ Adjusted for gender, BMI and TB contact history.

^# Adjusted for age, BMI and gender.

^* Adjusted for age, TB contact history and gender.