The scales "motivation", "capability" and "planning", which were created to assess the individual determinants of compliance with SSI prevention measures,15 proved to be valid and reliable for both physicians and nurses. Neither validity nor reliability could be demonstrated for the scale to assess the environmental determinants. Due to the sample recruitment in six hospitals, the data has a hierarchical structure. Presumably, the assessment of the environmental determinants was influenced more by hospital-specific characteristics than that of the individual determinants. This could have led to the participants' responses to the external determinants being more inconsistent across all hospitals. However, due to the sample size, the CFA could not be conducted in subgroups per hospital. As previous studies have emphasized the importance of environmental determinants of IPC compliance,24-27 developing valid and reliable measures of environmental determinants remains an important task.
Whereas in original COM-B terminology, planning represents a facet of motivation,10 CFA results replicated “planning” as an independent construct.15 Action and coping planning, a cognition oriented toward the implementation of behavior, seems to stand out as a specific determinant of (at least self-reported) behavior, especially given the large number of SSI prevention measures. In addition, the mean values for "planning" for physicians and nurses were by far the lowest of all the scales (see Table 3 and Supplementary_file_1). It appears that HCW have high intentions to comply with SSI prevention guidelines, but do not adequately plan how to translate this motivation into actual behavior. To help HCW overcome this intention-behavior gap, 28-29 tailored implementation interventions may specifically address action and coping planning to promote compliance. In general, we emphasize that this result should not be considered as an extension of the COM-B model, even though the labels "motivation" and "capability" have been retained for the other factors representing individual determinants.
Unlike previous studies,24-27,30 physicians and nurses in this sample did not differ in psychosocial determinants of compliance. By identifying ME between physicians and nurses, comparisons of scale means between these groups are unbiased and can be meaningfully interpreted. This raises the question of whether the differences found in previous studies are spurious.31 In other words, if questionnaires with no or inadequate ME have been used, any differences found in the determinants of compliance may be due to different understandings of the items and may not reflect true differences in the underlying construct. On the other hand, existing differences may not be found due to a lack of, or insufficient, ME. This supports the call for greater attention to issues of construct validity in IPC research, 32 not only in measuring compliance, but also in measuring the determinants of compliance.
Although physicians and nurses did not differ in self-reported compliance rate, differences were found in the regressions modeling self-reported compliance. For physicians, the explained variance of compliance was <10% and no regressor showed a significant relationship. In contrast, for nurses, the final model explained over 25% of the variance, and "planning" and "capability" showed a significant influence. Considering that self-reported compliance was similar in both groups and that observed compliance is consistently lower among physicians,1-3,33 these differences in determinants predicting compliance can be interpreted in three different ways. First, the determinants may be less predictive of physicians' self-reported compliance because their overestimation is greater than that of nurses,33 and thus these self-reports do not reflect compliance but rather overestimation. Second, the individual facets of the COM-B model may simply be not that relevant to physicians’ compliance, at least when measured with the scales used here. This would be consistent with the limited success of previous research in promoting physician IPC compliance,1-3,7,17 and raising the question of which factors are relevant to physicians. Third, there is the possibility that things are more chaotic than theory suggests, that is highly context-specific and/or dependent on unknown factors. This would be supported by the fact that the regression results for physicians in a university orthopedic hospital15 were similar to those for nurses in this non-university sample. The 'chaos' may highlight the need to tailor any intervention to promote compliance to the situation 'on the ground' in an even more careful way. This could be demonstrated by studies linking data on psychosocial determinants to observed compliance at the individual level of each HCW. However, such designs face ethical and data protection barriers.
This study has several strengths, including being confirmatory not only by its statistical approach but also by replicating previous analyses15 and, to our knowledge, being the first study examing the ME of psychosocial determinants of compliance with IPC measures.
Nevertheless, the study has some limitations. To begin with, the survey response rate was just above 30%, which was lower than the global average of 53% among surgical physicians.34 This led to a nearly undersized sample for the MGCFA among physicians. Probably questionaire length, as well as the lack of tangible incentives and questionnaire personalization,35 affected the response rate. The earlier study achieved a response rate of 73% among surgical physicians, likely due to the fact that healthcare professionals in a university hospital demonstrate a higher affinity for research and the study received exceptional support from the medical director.15 While efforts should be made to increase response rates, there is a declining trend in response rates among surgical physicians,35 and the current rate is at least within one standard deviation of the 2019 mean.35
Second, the 18 COM items represent only a sample of facets of all compliance determinants. For example, the Theoretical Domains Framework, the most integrative and granular classification of theoretical constructs relevant to behavior change, maps 84 constructs into 14 domains.36 Nevertheless, all of these 84 constructs can be mapped onto the COM components.36 The present items therefore reflect the need for a concise survey instrument. The selection of the most relevant facets was based on the best available evidence and the expertise of the transdisciplinary WACH study group.
Third, the items used to collect the determinants referred to all prevention measures within the participant's area of responsibility. It could be argued that this may bias the relationship between the determinants and the overall compliance score. Models such as the COM-B model were developed to identify determinants of individual behaviors in order to design behavior change interventions. However, different determinants may be important for different behaviors.10 While this argument certainly holds validity, a key trend in SSI prevention has been the use of bundles,37-39 i.e., sets of “…evidence-based interventions...that, when implemented together, will result in significantly better outcomes than when implemented individually”.40,p. 2 Compliance is therefore increasingly defined and measured on the basis of more than one measure. In this sense, the operationalization of SSI prevention compliance used in this study may be seen as a kind of "subjective bundle" approach. However, we acknowledge that such bundles may need unbundling to describe specific interventions to promote compliance.
Fourth, no specific direction of causality could be established because of the cross-sectional design of this observational study. Thus, the use of the scales in longitudinal studies is necessary to assess their causal structure and sensitivity to change.
Finally, the data were collected before the COVID-19 pandemic. Physicians and nurses may now differ in self-reported compliance and COM factors. However, the results of CFA and MGCFA, i.e., the evidence base for the validity, reliability, and ME of the scales, should be robust because these statistical analyses are based on the structure of the item responses, not the item scores themselves.
In summary, this study provides scales to assess capability, motivation, and action and coping planning as individual determinants of compliance to SSI prevention measures. As scales with proven ME among physicians and nurses, they allow a valid interpretation of group comparisons, at least for the original German version. Thus, they contribute to the understanding of how and why healthcare professions (do not) differ in IPC compliance. In conclusion, the study contributes to physicians’ IPC compliance as a current key topic in this area7 and meets the demand for “…easy-to-use, valid tools to provide data on the factors that influence the…behavior of healthcare professionals”.8, p. 412