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Table 2 Methodological characteristics of the included trials

From: The effectiveness of high dose zinc acetate lozenges on various common cold symptoms: a meta-analysis

Study, Domain of interest Description
Petrus et al. 1998 [ 21 ]*  
Randomization Reported as a randomized trial, but the method of randomization was not described.
Allocation concealment Participants and personnel did not know to which group the participants were allocated.
Blinding of participants and personnel Reported as double-blind, which implies that participants and personnel were blinded.
Blinding of outcome assessment Blinded subjects recorded their symptoms every day.
Losses to follow-up 1 was lost to follow-up.
Prasad et al. 2000 [ 22 ]*  
Randomization A Research-Assistant was responsible for randomization. This person did not see the patients and was not involved in collection of clinical data. The subjects were randomized into zinc and placebo groups by the research assistant as they were recruited.
Allocation concealment Participants and personnel did not know to which group the participants were allocated.
Blinding of participants and personnel The Clinical Assistant who collected all of the clinical information and remained in touch with the subjects who were recruited for the study remained completely blinded regarding the contents of the zinc and placebo pills.
Blinding of outcome assessment Blinded participants completed daily logs.
Losses to follow-up 2 in the placebo group dropped out on day 2.
Prasad et al. 2008 [ 23 ]*  
Randomization A research consultant prepared the randomization code and the packages of medication. The packages were identical in appearance except for the randomization numbers. This person did not see the patients and was not involved in collection of clinical data. The subjects were randomized into zinc and placebo groups by the research assistant as they were recruited.
Allocation concealment Participants and personnel did not know to which group the participants were allocated.
Blinding of participants and personnel The Clinical Assistant who collected all of the clinical information and remained in touch with the subjects who were recruited for the study remained completely blinded regarding the contents of the zinc and placebo pills.
Blinding of outcome assessment Blinded participants completed daily logs.
Losses to follow-up No drop outs.
  1. *Additional information about the methods of [22,23] was received from Ananda Prasad on Dec 17, 2014 and of [21] from Kenneth Lawson on Jan 7, 2015.