Table 3.

Interaction between a Latent Tuberculosis Infection, HIV Serostatus of the Index Case, and Variable Modifiers^*

Stratified by	Proportion with Latent Tuberculosis Infection (% Prevalence)†		Stratum-Specific Crude RR‡ (95% CI)	P Value for Interaction	Stratum-Specific Adjusted RR‡§ (95% CI)
	Household Contacts of HIV-Seropositive Tuberculosis Cases	Household Contacts of HIV-Seronegative Tuberculosis Cases				P Value for Interaction after Adjustment
Sputum smear of index case				0.02		0.03
Positive	443/643 (68.9)	570/780 (73.1)	0.94 (0.86–1.04)		0.93 (0.85–1.01)
Negative	101/235 (57.0)	147/194 (75.8)	0.75 (0.63–0.90)		0.76 (0.64–0.90)
Stratum-specific RR (95% CI)	1.21 (1.02–1.43)	0.96 (0.86–1.08)
Lung cavitation of index case				<0.01		<0.01
Cavitary disease	314/394 (79.7)	498/666 (74.8)	1.07 (0.97–1.17)		1.03 (0.96–1.12)
Noncavitary disease	252/471 (53.5)	193/272 (71.0)	0.75 (0.65–0.87)		0.74 (0.65–0.85)
Stratum-specific RR (95% CI)	1.49 (1.30–1.71)	1.05 (0.95–1.17)

Definition of abbreviations: CI = confidence interval; RR = relative risk.

^*All proportions are the number of individuals with a positive tuberculin skin test stratified by the HIV serostatus of the index case and the interaction factor in the left-hand column. All variables not included here were tested for interaction and are included in Table E2.

^†Column totals may vary across characteristics because of missing values for some participants.

^‡The stratum-specific relative risk refers to the two proportions in that row. The reference category for each relative risk is the right-hand column: household contacts of HIV seronegative tuberculosis cases.

^§Adjusted for age, education level, and alcohol status of the household contact; sputum smear and cavitary status of the index case; and the number of individuals in the household. Age of household contacts and family size were added to the adjusted model as continuous variables.