A. Moore et al., DERIVING DICHOTOMOUS OUTCOME MEASURES FROM CONTINUOUS DATA IN RANDOMIZED CONTROLLED TRIALS OF ANALGESICS - VERIFICATION FROM INDEPENDENT DATA, Pain, 69(1-2), 1997, pp. 127-130
A previously established relationship for deriving dichotomous from co
ntinuous information in randomised controlled trials (RCTs) of analges
ics has been tested using an independent data set. Individual patient
information from 18 RCTs of parallel-group design in acute postoperati
ve pain (after abdominal, gynaecological and oral surgery) was used to
calculate the percentage of the maximum possible pain relief score (%
maxTOTPAR) and the proportion of patients with >50%maxTOTPAR for the d
ifferent treatments, The relationship between the measures was investi
gated in 85 treatments with over 3400 patients. In 80 of 85 treatments
(94%) agreement between calculated and actual number of patients with
>50%maxTOTPAR was within four patients per treatment and in 72 (85%)
was within three (average of 40 patients per treatment, range 21-58 pa
tients). Summing the positive and negative differences between actual
and calculated numbers of patients with >50%maxTOTPAR gave an average
difference of 0.30 patients per treatment arm. Reports of RCTs of anal
gesics frequently describe results of studies in the form of mean deri
ved indices, rather than using discontinuous events, such as number or
proportion of patients with 50% pain relief. Because mean data inadeq
uately describe information with a non-normal distribution, combining
mean data in systematic reviews may compromise the results. Showing th
at dichotomous data can reliably be derived from mean data in acute pa
in studies enables data published as means to be used for quantitative
systematic reviews which require data in dichotomous form.