Table 3.

Difference in Zinc Acetate Lozenge Efficacy Between Subgroups

Subgroup	No. Common Cold Patients	Effects in Subgroups
		RR	95% CI	Test of Interaction (P)
All participants	199	3.1	2.1–4.7
Age (yr)
17–27	100	2.4	1.5–3.6	0.15
28–61	99	3.8	2.5–5.9
Sex
Male	82	3.6	2.1–6.3	0.5
Female	117	2.9	1.8–4.8
Ethnic groupa
White	132	2.8	1.9–4.1	0.4
Black	47	3.7	2.0–6.9
Allergy
No	137	3.0	1.8–4.9	0.5
Yes	62	3.7	1.9–7.1
Smokerb
No	70	8.7	4.0–19	0.8
Yes	28	9.9	3.7–27
Severity of the Common Cold at the Baselinec
Below median	102	4.0	2.3–6.9	0.2
Above median	97	2.8	1.6–4.7

Abbreviations: CI, confidence interval; RR, rate ratio.

^aEthnic groups other than white or black were excluded from this comparison.

^bThe Petrus et al [11] study did not collect data on smoking. The RR estimates are based only on the 2 studies by Prasad et al [12, 13].

^cThe severity scales of the 3 trials were different, and, therefore, the severity of each study was dichotomized by its own median severity score. The common cold severity above median is ≥8 points in the Petrus et al [11] study, ≥11 points in the Prasad et al [12] study, and ≥8 points in the Prasad et al [13] study (see Supplementary File 1 for details).