On 2014 Dec 07, Harri Hemila commented:

Rerksuppaphol S, 2013 reports a highly significant baseline imbalance on age

Rerksuppaphol S, 2013 randomized 100 children to the zinc and placebo groups using blocks of two. According to their Table 1, average age was 10.0 yr (SD 0.5 yr) in the zinc group, but 11.4 yr (SD 0.8 yr) in the placebo group; the authors calculated P=0.0001 for the difference in baseline age. In their paper, Rerksuppaphol S, 2013 do not comment on their calculation of highly significant imbalance on age.

As the most interesting finding, Rerksuppaphol S, 2013 report that coughs and runny noses were shorter in the zinc group, with P=0.01. The median “duration for cough” was 1.0 days in the zinc group, and 6.0 days in the placebo group. The total duration of the trial was 3 months and it seems obvious that many participants had more than 1 cold episode per 3 months. However, the Methods and Results do not describe whether the “duration of cough” means duration per episode or duration per person. Thus the outcomes are not well described. Given the reported baseline imbalance and the lack of transparency in the outcomes, it is difficult to trust the reporting on coughs and runny noses.

Rerksuppaphol S, 2013 refer to the Cochrane review on zinc for the common cold by Marshall I, 2000 (ref. 19), which was withdrawn several years ago in Marshall I, 2007. Thereafter a new Cochrane review was written by Singh M, 2011 which is also cited (ref. 25), without any mention that the latter replaced the old withdrawn Cochrane review (2000), which was also cited (ie ref. 19). Such a presentation of previous literature on zinc and colds gives an impression of sloppiness.

Rerksuppaphol S, 2013 has been cited in JAMA by Das RR, 2014. Therefore the validity of this study is a relevant issue.

On 2014 Dec 07, Harri Hemila commented:

Rerksuppaphol S, 2013 reports a highly significant baseline imbalance on age

Rerksuppaphol S, 2013 randomized 100 children to the zinc and placebo groups using blocks of two. According to their Table 1, average age was 10.0 yr (SD 0.5 yr) in the zinc group, but 11.4 yr (SD 0.8 yr) in the placebo group; the authors calculated P=0.0001 for the difference in baseline age. In their paper, Rerksuppaphol S, 2013 do not comment on their calculation of highly significant imbalance on age.

As the most interesting finding, Rerksuppaphol S, 2013 report that coughs and runny noses were shorter in the zinc group, with P=0.01. The median “duration for cough” was 1.0 days in the zinc group, and 6.0 days in the placebo group. The total duration of the trial was 3 months and it seems obvious that many participants had more than 1 cold episode per 3 months. However, the Methods and Results do not describe whether the “duration of cough” means duration per episode or duration per person. Thus the outcomes are not well described. Given the reported baseline imbalance and the lack of transparency in the outcomes, it is difficult to trust the reporting on coughs and runny noses.

Rerksuppaphol S, 2013 refer to the Cochrane review on zinc for the common cold by Marshall I, 2000 (ref. 19), which was withdrawn several years ago in Marshall I, 2007. Thereafter a new Cochrane review was written by Singh M, 2011 which is also cited (ref. 25), without any mention that the latter replaced the old withdrawn Cochrane review (2000), which was also cited (ie ref. 19). Such a presentation of previous literature on zinc and colds gives an impression of sloppiness.

Rerksuppaphol S, 2013 has been cited in JAMA by Das RR, 2014. Therefore the validity of this study is a relevant issue.