Seeking a simple measure of analgesia for mega-trials: is a single global assessment good enough?

We sought to investigate the potential of using a simple global estimation ('How effective do you think the treatment was?') as a measure of efficacy by comparing it with at least 50%maxTOTPAR (at least 50% of the maximum possible pain relief) in acute pain studies. One hundred and fifty randomized, double-blind trials included in 11 systematic reviews of single dose, oral analgesics for postoperative pain were used as a source of data. The relationship between the proportion of patients reporting the top two or three values on a five-point global scale and the proportion with at least 50%maxTOTPAR was investigated. Twenty-six trials provided data on the proportion reporting the top two categories (very good or excellent) and 27 gave data on the top three categories (good, very good or excellent). The relationship between the percentage of patients recording the top two categories on a five-point global scale and the proportion with at least 50%maxTOTPAR was fair (r(2)=0.67). That for the top three categories was less good (r(2)=0.57). Similar numbers-needed-to-treat were calculated for aspirin 600/650 mg and ibuprofen 400 mg using at least 50%maxTOTPAR and the top two categories. No real difference was seen in the correlation for standard wording compared to non-standard wording. Individual patient data were also used from four randomized, placebo-controlled, double-blind trials in postoperative pain. The frequency distribution for %maxTOTPAR was plotted for patients reporting each of the five categories on the global scale. A global assessment provides similar measures of analgesic efficacy as TOTPAR derived from hourly measurements, but the effects of adverse effects have yet to be understood.