Table 5.

Relative risks and attributable risk of tuberculosis infection conversion (TBIC) in the cohort study following vitamin D status by Poisson regression

Stratum	TBIC cases	Non-cases	Total	RR (95% CI)	AR (%)* (95% CI)
High exposure and TB sputum AFB-positive index case = 1
Vitamin D <20 ng/ml	1	1	2	2·75
Vitamin D ⩾20 ng/ml	2	9	11	(0·25–30·32)
High exposure and TB sputum AFB-positive index case = 0
Vitamin D <20 ng/ml	10	49	59	4·27
Vitamin D ⩾20 ng/ml	5	121	126	(1·46–12·5)
Adjusted results by Poisson regression				3·96 (1·51–10·37)	45·7% (20·6–55·2)

AFB, Acid-fast bacilli; RR, relative risk; AR, attributable risk; CI, Confidence interval; TB, tuberculosis.

^*Formula attributable risk: pd (RR – 1)/RR (where pd÷proportion of cases with vitamin D <20 ng/ml): 11/18 = 0·61.