Validity of QuickDASH at day of surgery versus day of initial consultation: Does informed consent make a difference?

Defining and evaluating the Hawthorne effect in primary care, a systematic review and meta-analysis

In 2015, we conducted a randomized controlled trial (RCT) in primary care to evaluate if posters and pamphlets dispensed in general practice waiting rooms enhanced vaccination uptake for seasonal influenza. Unexpectedly, vaccination uptake rose in both arms of the RCT whereas public health data indicated a decrease. We wondered if the design of the trial had led to a Hawthorne effect (HE). Searching the literature, we noticed that the definition of the HE was unclear if stated. Our objectives were to refine a definition of the HE for primary care, to evaluate its size, and to draw consequences for primary care research. We designed a Preferred Reporting Items for Systematic reviews and Meta-Analyses review and meta-analysis between January 2012 and March 2022. We included original reports defining the HE and reports measuring it without setting limitations. Definitions of the HE were collected and summarized. Main published outcomes were extracted and measures were analyzed to evaluate odds ratios (ORs) in primary care. The search led to 180 records, reduced on review to 74 for definition and 15 for quantification. Our definition of HE is "an aware or unconscious complex behavior change in a study environment, related to the complex interaction of four biases affecting the study subjects and investigators: selection bias, commitment and congruence bias, conformity and social desirability bias and observation and measurement bias." Its size varies in time and depends on the education and professional position of the investigators and subjects, the study environment, and the outcome. There are overlap areas between the HE, placebo effect, and regression to the mean. In binary outcomes, the overall OR of the HE computed in primary care was 1.41 (95% CI: [1.13; 1.75]; I 2 = 97%), but the significance of the HE disappears in well-designed studies. We conclude that the HE results from a complex system of interacting phenomena and appears to some degree in all experimental research, but its size can considerably be reduced by refining study designs.

Hawthorne effect on surgical studies

BACKGROUND

The Hawthorne effect or 'observer effect' describes a change in normal behaviour when individuals are aware they are being observed. This may have an impact on effect estimates in clinical trials. The purpose of this study was to determine if the Hawthorne effect had been recorded as a risk of bias in surgical studies.

METHODS

A Preferred Reporting Items for Systematic Reviews and Meta-Analyses compliant literature search was conducted till March 2019. Eligible studies included those reporting or not reporting the Hawthorne effect in surgical studies from the following databases: MEDLINE, Embase, CINAHL, AMED, BNI, HMIC, PsycINFO, Web of Science, Cochrane Library, Google Scholar and OpenGrey. Two reviewers independently reviewed the papers, extracted data and appraised study methods using the Newcastle Ottawa Scale or the Cochrane risk of bias tool. Data were analysed descriptively.

RESULTS

A total of 842 papers were identified, of which 16 were eligible. Six (37%) observational studies were identified with the aim of measuring the Hawthorne effect on their outcome with five reporting that the Hawthorne effect was responsible for the improvements in outcomes and one reporting no change in outcome due to the Hawthorne effect. Ten (63%) studies were identified, of which eight used the Hawthorne effect as an explanation to improvements seen in the control group or their secondary outcomes and two to compare their results with other studies.

CONCLUSION

There is considerable between-study heterogeneity on how the Hawthorne effect relates to surgical outcomes. Further consideration on reporting and considering the importance of the Hawthorne effect in the design of surgical trials is warranted.