Use of exercise tests in primary care: importance for referral decisions and possible bias in the decision process; a prospective observational study Gunnar Nilsson1, 2; Thomas Mooe1; Lars Söderström2; Eva Samuelsson1 1. Department of Public Health and Clinical Medicine, Umeå University, Umeå, Sweden; 2. Unit of Research, Education and Development – Östersund Hospital, Östersund, Sweden. Aim: We evaluated the results of exercise tests for selection of patients to cardiologic care, and if referral decisions were biased by sex, socioeconomy or age. Methods : Primary care patients, 438 men and 427 women, with exercise testing for suspected coronary disease. Referrals to cardiologist were registered within six months from exercise testing. Predictive variables were identified by multivariable logistic regression. Socioeconomy was assessed by education and employment grade.

Results Patients with positive, non conclusive or negative exercise tests were referred to cardiologist in 67.3%, 26.1% and 3.5%, respectively. Overall, there was no significant difference in referral rates, related to gender or socio-economic level. Self employment predicted referral in women. Among non-manual employees, male patients were referred more frequently. Positive/non conclusive exercise tests and exertional chest pain predicted referral in both sexes. In patients with a positive exercise test, referral rates decreased with age, adjusted for previous revascularization, myocardial infarction, transitory ischaemic attack, stroke or exertional chest pain (OR 0.48, 95% CI 0.23-0.97; p=0.042). Cardiovascular events occurred in 22.2% of non-referred patients with a positive exercise test. These patients were not considered for cardiologic care in 56% of cases.

Table 1 Adjusted ORs for referral to cardiologist according to patient characteristics in women and menmen Women (n=427) Men (n=438) OR (95% CI) P Positive/inconclusive exercise test 11.07 (5.11-23.95) <0.001 13.60 (6.77-27.33) Exertional chest pain 2.40 (1.03-5.63) 0.043 3.22 (1.52-6.85) 0.002 Pathologic ST-T segment on resting ECG - NS 2.42 (1.07-5.49) 0.034 Previous revascularisation 5.15 (1.33-19.97) 0.018 Self-employed 3.92 (1.29-11.92) 0.016 Age 0.99 (0.96-1.03) 0.589 1.01 (0.98-1.04) 0.655 Characteristics remaining significant in a multivariable analysis adjusted for age. Follow-up within six months of exercise testing. NS=not significant.

Employment Employed Self-employed Female Male Table 2 Adjusted ORs (95% CIs) for referral to cardiologic evaluation, by sex and employment Employment Employed Self-employed Female 1.00 (n=352) 3.62 (1.19-10.99) (n=32) Male 1.73 (0.99-3.01) (n=332) 1.87 (0.76-4.61) (n=77) Referrals took place within six months from exercise testing. Employed females served as reference. ORs were adjusted for age, exertional chest pain, and positive/inconclusive exercise test result versus negative test.

Conclusion & Clinical Relevance Table 3 Patients with positive exercise tests, by age and referral to cardiologic evaluation within six months Age in years Exercise test positive Referred to cardiologist (%) Not referred to cardiologist (%) 40-49 4 (100%) 0 (0%) 50-59 5 (83.3%) 1 (16.7%) 60-69 14 (73.7%) 5 (26.3%) 70-79 12 (57.1%) 9 (42.9%) 80-89 2 (40%) 3 (60%) All ages 37 (67.3%) 18 (32.7%) Fifty-five primary care patients with positive exercise tests, of 865 patients examined; two-sided test for trend, p=0.024. Gender and socio-economy interactions affected the referral rates, after exercise testing. In patients with a positive exercise test, referral rates decreased with age. Exercise tests are important to select patients to cardiologic care. An increased awareness of possible bias regarding age, gender and socioeconomy is necessary.

Table 3 Patients with positive exercise tests, by age and referral to cardiologic evaluation within six months Age in years Exercise test positive Referred to cardiologist (%) Not referred to cardiologist (%) 40-49 4 (100%) 0 (0%) 50-59 5 (83.3%) 1 (16.7%) 60-69 14 (73.7%) 5 (26.3%) 70-79 12 (57.1%) 9 (42.9%) 80-89 2 (40%) 3 (60%) All ages 37 (67.3%) 18 (32.7%) Fifty-five primary care patients with positive exercise tests, of 865 patients examined; two-sided test for trend, p=0.024.

Conclusion & Clinical Relevance Gender and socio-economy interactions affected the referral rates, after exercise testing. In patients with a positive exercise test, referral rates decreased with age. Exercise tests are important to select patients to cardiologic care. An increased awareness of possible bias regarding age, gender and socioeconomy is necessary.