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- Published on: 8 April 2021
- Published on: 8 April 2021Questionable reliability of the zinc results
To the editor and authors,
We have several concerns about the zinc results in this systematic review
1. Weismann et al. 1990 RCT evaluates zinc for treating, not preventing infections, yet is included in the prevention meta-analyses (Figure-6).
2. Farr et al. 1987 reports post-exposure prophylactic and treatment results for two RCTs. Which RCT was used? Why was the other ignored? Supp-Table-5 reports an incorrect sample size and MD rather than RR. The validity of combining pre- and postexposure prophylactic trials is questionable and at the very least, should be discussed.
3. Turner et al. 2000 reports two RCTs, both had 4 arms. Why was one RCT and two of the three zinc arms ignored? If these arms were included, an explanation for how the means (SDs) were combined is missing.
4. Table 3 lacks transparency as the studies used in each subgroup are not cited and often it is unclear what data was used. For example, none of the five RCTs included in the zinc prevention meta-analysis reported infection rates for males and females, yet this is reported.
5. The authors claim there was no evidence of a dose response for zinc used for treatment. Only two RCTs evaluated a dose ≤13.3mg/day. Both used intranasal sprays/gels. All other treatment studies evaluated lozenges. Comparing doses for different administration routes is clinically meaningless. All this analysis tells us is there is no difference between intranasal and sublingual adminis...
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None declared.