Aim: The original purpose of this study was to determine the Minimal Important Difference for the Asthma Control Questionnaire (ACQ) but an unexpected tendency of clinicians to overestimate improvements in asthma control thwarted the endeavour. We describe the observed clinician bias and discuss its implications for clinical practice and research.
Methods: Ninety-four adults with inadequately controlled asthma received a full clinical consultation with one of nine asthma specialists. Medications were adjusted according to clinical needs. Four weeks later the same clinician estimated change in asthma control on a 15-point scale (-7 = a very great deal worse, 0 = no change, +7 a very great deal better). All patients completed the ACQ before each consultation but responses were not shown to the clinician.
Results: Clinicians consistently recorded that patients improved more than their change in ACQ scores suggested (p = 0.018).
Conclusion: Clinicians should be aware of potential biases that may occur when estimating change in asthma control compared with measuring absolute status at each visit.