A prospective study of patients' pain intensity after cardiac surgery and a qualitative review: effects of examiners' gender on patient reporting.

Background and aims As indicated by experimental studies, reports of pain intensity may depend on the examiner's gender. Until now, it is unclear whether this is relevant in clinical routine. This study investigated prospectively whether the gender of assessor plays a role in patients' pain reports and whether this role differs in male and female patients. Methods 165 patients (66.4 years±0.63; 118 males) scheduled for heart surgery were allocated consecutively to one examiner out of four students of both genders: two females and two males (aged 24.3 years±1.7). Therefore, the following study groups were defined: Group 1: female assessors-female patients, 2: female-male; 3: male-female, 4: male-male. Using a standardized analgesic scheme, patients were asked to rank their pain intensity on a numeric rating scale (NRS: 0-10), postoperatively. Statistics: Kruskal-Wallis, Mann-Whitney; p<0.05. Additionally, a qualitative literature review of the databases Medline and CENTRAL was performed focusing on experimental and clinical studies on experimenter gender bias. Due to the review, this prospective clinical study was designed to investigate whether patients after surgery report lower pain intensities when assessed by a female compared to a male assessor. Results Summarizing all patients, pain intensity on POD_1 was rated 4.0±2.4 on NRS and decreased on POD_2 to 3.0±2.1 [H(3)=37.941, p=0.000]. On average, pain intensity did not differ between males and females (NRS: 3.5 vs. 3.6). Only on the second postoperative day, more intense pain was reported in front of female assessors and less intense pain in front of male assessors (NRS: 3.4 vs. 2.4; p=0.000). A main effect for the four groups was seen (p=0.003): male patients reported higher pain scores to female assessors (NRS: 3.5 vs. 2.3; p=0.000). Conclusions Together, contrary to the expectations, patients after cardiac surgery reported a higher pain intensity in front of a female and a lower pain intensity in front of a male assessor. In particular, female caregivers may heighten the reported pain intensity up to 1.2 NRS-points; this bias seems to be more relevant for male patients. Implications Therefore, despite some methodological weakness, our data suggest that attention should be paid to a rather small, but somehow significant and consistent examiner gender bias after cardiac surgery especially in male patients. Further clinical studies are needed to show the true extent of clinical relevance and exact mechanisms underlying these gender reporting bias.