Journal of clinical epidemiology
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We performed a cross-cultural adaptation of the McGill Pain Questionnaire (MPQ) from English to Spanish for studying Mexican Americans in South Texas. Each of the 78 single-word pain descriptors in the original MPQ was translated into Spanish by a panel of nine bilingual health researchers, preserving the original structure of the questionnaire. The pain-intensity content (PIC) of the words in each language was then rated on a 100 mm visual analog scale by 8 bilingual health care providers and 10 bilingual health-care consumers. ⋯ Test-retest reliability of the Spanish and English components of the MPQ was not significantly different and was comparable to that of the other pain and health status instruments. We conclude that the Spanish MPQ is cross-culturally equivalent to the original English and has similar concurrent validity and reliability. This questionnaire is suitable for cross-cultural studies of pain comparing Spanish-speaking Mexican Americans with English-speaking members of the same and other ethnic groups.
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We performed a Monte Carlo study to evaluate the effect of the number of events per variable (EPV) analyzed in logistic regression analysis. The simulations were based on data from a cardiac trial of 673 patients in which 252 deaths occurred and seven variables were cogent predictors of mortality; the number of events per predictive variable was (252/7 =) 36 for the full sample. For the simulations, at values of EPV = 2, 5, 10, 15, 20, and 25, we randomly generated 500 samples of the 673 patients, chosen with replacement, according to a logistic model derived from the full sample. ⋯ For EPV values of 10 or greater, no major problems occurred. For EPV values less than 10, however, the regression coefficients were biased in both positive and negative directions; the large sample variance estimates from the logistic model both overestimated and underestimated the sample variance of the regression coefficients; the 90% confidence limits about the estimated values did not have proper coverage; the Wald statistic was conservative under the null hypothesis; and paradoxical associations (significance in the wrong direction) were increased. Although other factors (such as the total number of events, or sample size) may influence the validity of the logistic model, our findings indicate that low EPV can lead to major problems.