THE ASSOCIATION BETWEEN LOCAL DIAGNOSTIC TESTING INTENSITY AND INVASIVE CARDIAC PROCEDURES

Objective.-To determine the extent to which geographic variation in in vasive cardiac procedures can be explained by the variable use of diag nostic testing. Design.-A population-based cohort study using Medicare Part B data (physician services). Setting and Subjects.-Procedure dat a for all Medicare beneficiaries in northern New England. Main Outcome Measures.-Twelve coronary angiography service areas were constructed for Medicare beneficiaries in northern New England. Age- and sex-adjus ted utilization rates were developed for three procedure categories: t otal stress test, coronary angiography, and revascularization. Total s tress tests were further stratified into nonimaging and imaging proced ures leg, thallium). Tests performed in follow-up to invasive procedur es were excluded leg, stress test following revascularizations). Linea r regression was used to assess the relationship between procedure cat egories. Results.-A tight positive relationship was found between tota l stress test rates and the rates of subsequent coronary angiography ( R(2)=0.61, P<.005). Most of the variance was explained by imaging stre ss tests (R(2)=0.50, P<.02), A strong relationship was found between c oronary angiography and revascularization (R(2)=0.82, P<.001). Finally , a clear relationship between total stress tests and subsequent revas cularizations was also found (R(2)=0.55, P<.006). Conclusion.-The popu lation-based rates of diagnostic testing largely explained the varianc e associated with subsequent therapeutic interventions. Our results su ggest that local testing intensity is an important determinant of the variable use of invasive cardiac procedures.