An evaluation of cusum analysis in asthma.

It has been claimed that cusum analysis may be a clearer way of expressing trends in serial peak flow (PF) measurements in asthma than visual inspection of peak flow charts. To assess this we have applied cusum analysis to serial PF measurements in patients receiving various forms of treatment for airflow obstruction. We found that cusum analysis usually gave no additional advantage over simple graphs of PF data. In cases in which trends were apparent only by cusum analysis, their dimension was such that they were unlikely to form the basis of decisions on treatment.