Assessment of recovery status in chronic fatigue syndrome using normative data.

Abstract

Adamowicz et al. have reviewed criteria previously employed to define recovery in chronic fatigue syndrome (CFS). They suggested such criteria have generally lacked stringency and consistency between studies and recommended future research should require "normalization of symptoms and functioning". Options regarding how "normalization of symptoms and functioning" might be operationalized for CFS cohorts are explored. A diagnosis of CFS excludes many chronic disabling illnesses present in the general population, and CFS cohorts can almost exclusively consist of people of working age; therefore, it is suggested that thresholds for recovery should not be based on population samples which include a significant proportion of sick, disabled or elderly individuals. It is highlighted how a widely used measure in CFS research, the SF-36 physical function subscale, is not normally distributed. This is discussed in relation to how recovery was defined for a large intervention trial, the PACE trial, using a method that assumes a normal distribution. Summary data on population samples are also given, and alternative methods to assess recovery are proposed. The "normalization of symptoms and function" holds promise as a means of defining recovery from CFS at the current time. However, care is required regarding how such requirements are operationalized, otherwise recovery rates may be overstated, and perpetuate the confusion and controversy noted by Adamowicz et al.