Table 4:

Logistic regression models of factors associated with CT, Zambian HRW, 2016

	Bivariate Association				Multivariate Final Modelb
Predictor of CTa	Odds Ratio	Lower 95% CI	Upper 95% CI	p-Value	Adj. Odds Ratio	Lower 95% CI	Upper 95% CI	Adj. p-Value
Age Group
Age 18–24	1.76	1.08	2.85	0.02	2.05	1.13	3.72	0.02
Age 25+	ref	-	-	-	ref	-	-	-
Literacy
Reads English, Bemba, or Nyanja	ref	-	-	-	ref	-	-	-
Illiterate	0.64	0.40	1.00	0.05	0.48	0.26	0.89	0.02
Education × City
No School or Primary School Only vs Secondary School or Higher in Lusaka	2.26	1.03	4.99	0.04	4.46	1.42	13.98	0.01
No School or Primary School Only vs Secondary School or Higher in Ndola	0.90	0.51	1.61	0.73	1.25	0.62	2.54	0.53
Unprotected Sex (Last 1–3 months) × City
At least once vs None in Lusaka	3.72	1.39	9.96	0.01	4.38	1.44	13.30	0.01
At least once vs None in Ndola	1.51	0.77	2.96	0.23	1.37	0.68	2.76	0.38
Uses LARC Method × City
Uses Implant or IUD vs No LARC in Lusaka	0.37	0.13	1.02	0.06	0.14	0.03	0.69	0.02
Uses Implant or IUD vs No LARC in Ndola	2.43	1.41	4.2	<0.01	2.22	1.17	4.20	0.01

Adj, adjusted; CI, confidence interval; CT, Chlamydia trachomatis; HRW, high-risk women; LARC, long-acting reversible contraception; IUD, intrauterine device; ref, reference group.

^aThe following variables were not significant in bivariate analyses and are not tabled: cohort, sex in exchange for money, pregnancy, HIV rapid test result, sperm (microscopy), candida (microscopy), BV, and new syphilis infection.

^bStepwise model selection done in both directions using the stepAIC function in R. The following variables were not significant in initial adjusted analyses and were removed from the final multivariate model via bi-directional stepwise selection and are not tabled: age group × city, literacy × city, TV, and TV × city. The final model contained 529 observations, including 68 with the outcome of interest.