Table 2.

Logistic regression results showing odds of disease (specific disorder) when injecting in the legs vs. injecting in the arms (3 vs. 2) and odds of disease when injecting in the legs vs. noninjecting (3 vs. 1)

		Hypothesis test				95% Wald’s confidence interval for odds
Specific disorder of the legs	Comparison	Wald’s Chi-square	df	Significance	Odds	Lower	Upper
Malleolar flare	3 vs. 1	5.15	1.00	0.02	1.68	1.07	2.63
	3 vs. 2	0.51	1.00	0.48	1.17	0.76	1.80
Telangiectasis	3 vs. 1	0.33	1.00	0.57	1.11	0.78	1.59
	3 vs. 2	0.44	1.00	0.51	1.13	0.78	1.64
Reticular veins	3 vs. 1	1.98	1.00	0.16	1.30	0.90	1.87
	3 vs. 2	0.00	1.00	0.98	1.01	0.69	1.46
Varicose veins	3 vs. 1	7.51	1.00	0.01	1.69	1.16	2.46
	3 vs. 2	9.09	1.00	< 0.001	1.82	1.23	2.68
Edema	3 vs. 1	20.56	1.00	< 0.001	2.37	1.63	3.44
	3 vs. 2	30.04	1.00	< 0.001	2.94	2.00	4.33
Pigmentation	3 vs. 1	57.01	1.00	< 0.001	7.35	4.38	12.34
	3 vs. 2	35.06	1.00	< 0.001	4.21	2.62	6.78
Eczema	3 vs. 1	16.94	1.00	< 0.001	5.77	2.51	13.30
	3 vs. 2	6.74	1.00	< 0.001	2.44	1.25	4.79
Lipodermatosclerosis	3 vs. 1	20.97	1.00	< 0.001	29.11	6.88	123.23
	3 vs. 2	18.40	1.00	< 0.001	6.82	2.84	16.40
Scars from healed ulcers	3 vs. 1	24.77	1.00	< 0.001	36.86	8.90	152.57
	3 vs. 2	26.80	1.00	< 0.001	7.39	3.46	15.75
Active ulcers	3 vs. 1	12.10	1.00	< 0.001	34.64	4.70	255.16
	3 vs. 2	13.26	1.00	< 0.001	9.14	2.78	30.06

Logistic regression was performed on each leg disorder separately while controlling for age and comorbidities. The predictor, site of injection/noninjection drug use group, was coded with Category 3 as the reference category. Because the odds ratio is symmetric, reversing the reference category of the outcome resulted in the contrasts indicated.