The Hawthorne effect on adherence to hand hygiene in patient care.

Numerous studies demonstrate that the Hawthorne effect (behaviour change caused by awareness of being observed) increases health workers' hand hygiene adherence but it is not clear whether they are methodologically robust, what the magnitude of the effect is, how long it persists or whether it is the same across clinical settings. The objective of this review was to determine the rigour of the methods used to assess the Hawthorne effect on hand hygiene, effect size estimation, variations between clinical settings and persistence. To this end, a systematic literature review with meta-analysis was conducted. Nine studies met the criteria for the review. Methodological quality was variable. The Hawthorne effect ranged from -6.9% to 65.3%. It was 4.2% in one study conducted in intensive care and 16.4% in transplant units. It was most marked when data were collected across an entire hospital and in a group of general hospitals. Differences between wards in the same hospital were apparent. In the two studies where duration was estimated, the Hawthorne effect appeared transient. Despite methodological shortcomings, the review indicates clear evidence of a Hawthorne effect on general wards. There is evidence that it may vary between clinical speciality and across departments. The review identifies a need for standardized methodologies to measure the Hawthorne effect to overcome the dilemma of reporting the potentially inflated rates of adherence obtained through overt audit. Occasional covert audit could give a better estimation of true hand hygiene adherence but its acceptability and feasibility to health workers need to be explored.