Table 2.

Demographic, clinical, and social characteristics of tuberculosis (TB) cases identified as contacts (contact cases) to infectious TB cases (index cases) by prevalence status^a, New York City, 1997–2007

	Prevalent contact cases		Incident contact cases
	N	%	N	%	P valueb
Total	70	100	48	100
Age group (years) at TB diagnosis
0–4	6	9	1	2	0·238
5–17	7	10	4	8	1·000
18–44	37	53	31	65	0·205
45–64	18	26	8	17	0·244
⩾65	2	3	4	8	0·223
Median age in years at TB diagnosis (range)	33 (0–95)		32·5 (4–81)		0·850
Female sex	33	47	19	40	0·417
US-bornc	37	53	19	40	0·156
Race/ethnicity (among US-born)
Black non-Hispanic	29	78	14	74	0·694
White non-Hispanic	6	16	2	11	0·565
Hispanic	1	3	1	5	0·625
Asian	1	3	2	11	0·218
Household exposure setting	52	74	29	60	0·111
Tuberculin skin test (TST) resultd
Positive	48	69	24	50	0·042
Negative	6	9	10	21	0·056
No TST administered: prior TB diagnosis	4	6	1	2	0·647
No TST administered: prior positive TST	8	11	4	8	0·759
Window negative	3	4	3	6	0·686
Not tested	1	1	6	13	0·018
TST converted from negative to positive
Eligiblee	8	11	14	29	n.a.
Converted (among eligible)	5	63	8	57	n.a.
Initial genotype concordance statusf
Exact match	55	78	28	58	0·018
Non-exact match	15	21	20	42
Final genotype concordance statusg
Exact or near-match	61	87	36	75	0·090
Discordant	9	13	12	25
HIV status at TB diagnosis
Infected	15	21	8	17	0·638
Not infected	46	66	31	65	0·899
Unknown	9	13	9	19	0·381
History of homelessness ever
Yes	1	1	7	15	0·008
No	6	9	21	44	<0·001
Missing	63	90	20	42	<0·001
History of illicit drug use ever
Yes	12	17	7	15	0·710
No	56	80	40	83	0·648
Missing	2	3	1	2	0·793

n.a., Not applicable.

^aPrevalent contact cases were diagnosed within 9 months of the date of diagnosis of the associated index case. Incident contact cases were diagnosed >9 months after the date of diagnosis of the associated index case.

^bP values generated by Pearson's χ² or Fisher's exact tests for proportions, Wilcoxon rank sum test for medians.

^cIncludes birth in US territories.

^dTST result when contact case was originally evaluated as a contact. Contacts that had a negative TST result in the window period (within 8 weeks of last known date of exposure) but did not have a subsequent test were assigned a window negative TST result.

^eContacts were eligible for TST conversion if they either had a known TST induration result within 2 years of the first TST after being identified as a contact, or if they had a negative (<5 mm induration) TST during the window period and then a second TST after the window period. An increase of 10 mm induration between the TST qualifies as a conversion.

^fContact case and index case genotypes are comprised of both spoligotype and IS6110 restriction fragment length polymorphism (RFLP) results. Genotype concordance was determined by comparing the genotypes of case-pairs (consisting of the contact case and the associated index case). Initially, genotypes that matched exactly were considered exact matches and all others were categorized as non-exact matches.

^gIn non-exact matches, contact cases were further categorized as either near-match (case-pair with the same spoligotype and RFLP patterns differing by ⩽2 bands). Non-exact matches that did not meet the near-match definition were classified as discordant.