To the Editor The JAMA Clinical Evidence Synopsis on zinc for the common cold by Drs Das and Singh1 was a summary of their Cochrane review.2 I noticed inconsistencies in the synopsis and so attempted to replicate their data.
In the Evidence Profile section of the synopsis, the authors stated that the number of randomized clinical trials included was “14 therapeutic (lozenges: low-dose = 5, high-dose = 7, syrup = 2) … and 2 prophylactic …,” which implies that the reported findings are purely based on randomized comparisons. However, their estimate of 3.43-day shorter colds for high-dose vs low-dose zinc lozenge users appears not to be based on a comparison of randomized groups but rather on an arbitrary selection of 5 high-dose zinc groups from 7 trials compared with 5 low-dose zinc groups from different trials.
Hemilä H. Common Cold Treatment Using Zinc. JAMA. 2015;314(7):730. doi:10.1001/jama.2015.8174