Single-blind trials

Ideally the trial should be double-blind with both the subject and the investigator being blind to the specific treatment allocation. If this is not possible for the investigator, for example, then the next best thing is to have an independent evaluation of outcome, both for efficacy and for safety. A single-blind trial arises when either the subject or investigator, but not both, is blind. 

In a randomized, single-blind trial of 40 patients receiving lithium or verapamil, Walton et al. ( 263) found lithium to be superior to verapamil on all measures. Potential confounding factors included the use of lorazepam throughout the study as a rescue medication given both intravenously and orally, a 1-day washout period, and the use of antipsychotic medications on the last day of the study. 

Walton S, Berk M, Brook S. Superiority of lithium over verapamil in mania a randomized, controlled, single-blind trial. J Clin Psychiatry 1996 57 543-546. 

In conjunction with randomization, a feature known as blinding helps ensure that bias doesn t distort the conduct of a trial or the interpretation of its results. Single-blinding means the participant does not know whether he or she is receiving the experimental drug, an established treatment for that disease, or a placebo. In a single-blinded trial, the research team does know what the participant is receiving. 

Singh, R. B., Dubnov, G., Niaz, M. A., Ghosh, S., Singh, R., Rastogi, S. S., Manor, O., Pella, D., and Berry, E. M. (2002). Effect of an Indo-Mediterranean diet on progression of coronary artery disease in high risk patients (Indo-Mediterranean Diet Heart Study) A randomised single-blind trial. Lancet 360, 1455-1461. 

In addition to manufacturing both the test drug and the comparator drug, these materials need to be blinded. A trial may be called a double-blind study when neither the subjects nor any of the people concerned with their evaluation and care know which treatment the subjects are receiving. While double-blind trials predominate, in some cases a single-blind trial is conducted if it is not possible to blind the subjects (or sometimes the investigators). When trials are conducted in which everyone knows what treatment a subject is receiving, the trial is said to be unblinded. 

P. F. Porciani, S. Grandini and S. Sapio (2003). Anticalculus efficacy of a chewing gum with polyphosphates in a twelve-week single-blind trial. J. Clin. Dent., 14, 45-47. 

Lebel MH, Mehra S. Efficacy and safety of clarithromycin versus erythromycin for the treatment of pertussis a prospective, randomized, single blind trial. Pediatr Infect Dis J 2001 20(12) 1149-54. 

Sprung J, Kindscher JD, Wahr JA, Levy JH, Monk TG, Moritz MW, O Hara PJ. The use of bovine hemoglobin glutamer-250 (Hemopure) in surgical patients results of a multicenter, randomized, single-blinded trial. Anesth Analg 2002 94(4) 799-808. 

Ondansetron and zacopride have been evaluated in acute schizophrenia. A double-blind, placebo-controlled trial with ondansetron has indicated a reduction in both positive and negative symptoms of schizophrenia [183], but one single-blind trial reported that zacopride was less effective [184] [for review see 236]. 

Effect of AA-344 on Asthma. In an earlier report (33), a single blind trial in l4 subjects with atopic bronchial asthma (paroxysmal or chronic type) was carried out and the efficacy was assessed subjectively from the alleviation of... 

In a 24-month, randomized, single-blind trial of botuhnum A in 10 children with Charcot-Marie-Tooth disease type lA aged 3-14 years the treated leg received intramuscular injections at 6-month intervals in the tibialis posterior and peroneus longus and the control leg received no injections [62 ]. The intramuscular injections proved safe and were weU tolerated but did not affect the progression of pes cavus. 

Comparative studies In a prospective single-blind trial in 125 randomized patients... 

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