Table 3.

Diagnosed tuberculosis in children during follow-up, stratified by child, maternal, and household characteristics

				Disease events*(n)	Partici-pants (n)	Child-years of obser-vation	Incidence per 100 child-years (95% CI)	HR (95% CI, p value)
All participants				81	915	2736·8	2·9 (2·4–3·7)	··
Child characteristics
	Sex
		Female		32	447	1355·3	2·4 (1·7–3·3)	1 (ref)
		Male		49	468	1381·5	3·5 (2·7 − 4·7)	1·50 (0·96–2·35, p=0·073)
	Birthweight†
			Normal	64	780	2331·1	2·7 (2·1–3·5)	1 (ref)
			Low	17	135	405·8	4·2 (2·6–6·7)	1·56 (0·91–2·66, p=0·10)
	Gestational age‡
		Full term		65	768	2298·0	2·8 (2·2 − 3·6)	1 (ref)
		Preterm		16	147	438·8	3·6 (2·2 − 6·0)	1·30 (0·76–2·25, p=0·34)
	Lower respiratory tract infection
		No		27	475	1502·0	1·8 (1·2 − 2·6)	1 (ref)
		Yes		54	440	1234·9	4·4 (3·3 − 5·7)	2·29 (1·44–1·64, p<0·0001)
	HIV status
		Negative		80	913	2731·8	2·9 (2·4 − 3·6)	1 (ref)
		Positive		1	2	5·1	19·8 (2·8 − 100·0)	6·42 (0·89–46·14, p=0·065)
	Weight-for-age Z score§
		Underweight		7	84	244·6	2·9 (1·4 − 6·0)	0·94 (0·43–2·04, p=0·88)
		Normal weight		73	812	2437·9	3·0 (2·4 − 3·8)	1 (ref)
		Overweight		1	15	41·1	2·4 (0·3 − 17·3)	0·75 (0·10–5·43, p=0·78)
	Breastfeeding
		Did not breastfeed		2	65	202·4	1·0 (0·2 −4·0)	1 (ref)
		Breastfed		79	850	2534·4	3·1 (2·5–3·9)	3·26 (0·80–13·36, p=0·10)
	Isoniazid preventive therapy
		Among converters
			No	43	117	261·6	16·4 (12·2–22·2)	1 (ref)
			Yes	2	33	110·1	1·8 (0·0–7·3)	0·13 (0·03–0·56, p=0·0058)
		Among non-converters
			No	33	737	2271·1	1·5 (1·0–2·0)	1 (ref)
			Yes	3	28	94·1	3·2 (1·0–9·9)	2·36 (0·72–7·67, p=0·16)
Maternal characteristics
	Age (years)			··	··	··	··	0·98 (0·94–1·02, p=0·37)
	Tuberculosis treatment in pregnancy
		No		75	874	2627·0	3·0 (2·3–3·6)	1 (ref)
		Yes		6	41	109·8	5·5 (2·5–12·2)	1·78 (0·78–4·09, p=0·17)
	Ever diagnosed with tuberculosis§
		No		79	874	2619·3	3·0 (2·4–3·8)	1 (ref)
		Yes		2	38	109·0	1·8 (0·4–7·3)	0·59 (0·14–2·39, p=0·46)
	Maternal smoking during pregnancy§¶
		No		46	692	2097·4	2·2 (1·6–2·9)	1 (ref)
		Yes		34	218	622·6	5·5 (3·9–7·6)	2·47 (1·58–3·85, p<0·0001)
	Maternal education§
		Primary school only		10	73	218·4	4·6 (2·5–8·5)	1 (ref)
		Some secondary school		45	500	1486·4	3·0 (2·3–4·1)	0·65 (0·33–1·29, p=0·22)
		Finished secondary school		26	342	1032·0	2·5 (1·7–3·7)	0·55 (0·26–1·13, p=0·11)
Household characteristics
	Socioeconomic status (quartile)§
		Lowest		24	233	726·6	3·3 (2·2–4·9)	1 (ref)
		Moderate low		23	242	712·2	3·2 (2·1–4·9)	0·94 (0·53–2·42, p=0·83)
		Moderate high		18	226	656·6	2·7 (1·7–4·4)	0·79 (0·43–1·46, p=0·46)
		Highest		15	206	614·9	2·4 (1·5–4·0)	0·72 (0·38–1·37, p=0·32)
	Clinic
		Mbekweni		26	495	1472·4	1·8 (1·2–2·6)	1 (ref)
		TC Newman		55	420	1264·4	4·3 (3·3–5·7)	2·55 (1·60–4·07, p<0·0001)
	Household income (rand per month)
		<1000		38	354	1114·1	3·4 (2·5–4·7)	1 (ref)
		1000–5000		38	442	1261·2	3·0 (2·2–4·1)	0·84 (0·53–1·31, p=0·43)
		>5000		5	114	361·5	1·4 (0·6–3·3)	0·41 (0·16–1·03, p=0·059)
	Crowding (people per household)§
		≤3		18	297	886·3	2·0 (1·3–3·2)	1 (ref)
		4–5		28	313	940·6	3·0 (2·1–4·3)	1·50 (0·83–2·70, p=0·18)
		>5		35	303	904·2	3·9 (2·8–5·4)	1·94 (1·10–3·42, p=0·022)
	Children younger than 5 years per household
		0		42	563	1705·4	2·5 (1·8–3·3)	1 (ref)
		1		31	291	851·5	3·6 (2·6–5·2)	1·45 (0·91–2·31, p=0·12)
		>1		8	61	179·9	4·4 (2·2–8·0)	1·75 (0·82–3·73, p=0·15)
	Patient with tuberculosis in household in past year§
		No		64	779	2386·1	2·7 (2·1–3·4)	1 (ref)
		Yes		15	128	329·5	4·6 (2·7–7·6)	1·52 (0·86–2·67, p=0·15)

Missing data are detailed in table 1. HR=hazard ratio.

^*Any tuberculosis diagnosis made in the clinic (clinically, radiographically, or microbiologically).

^†Normal birthweight is 2·5 kg or more and low birthweight is less than 2·5 kg.

^‡Full term is 37 weeks or more and preterm is less than 37 weeks.

^§Some data are missing for this variable.

^¶Self-reported smoking status at the baseline study visit; self-reported smoking was highly correlated with maternal cotinine levels