Effects of age on the performance of common diagnostic tests for pulmonary embolism

PURPOSE: The diagnosis of pulmonary embolism in the elderly is often difficult because of comorbid medical conditions, and perhaps also because diagnostic tests have a lower yield. We analyzed the diagnostic performance of common diagnostic tests for pulmonary embolism in different age groups. METHODS: We analyzed data from two large studies that enrolled 1,029 consecutive patients presenting to the emergency department with clinically suspected pulmonary embolism. The clinical probability of pulmonary embolism (high [≥80%], intermediate, or low [≤20%]) was estimated by the treating physician. All patients underwent a sequential diagnostic protocol, including ventilation-perfusion lung scan, measurement of plasma D-dimer level, lower limb venous compression ultrasonography, and pulmonary angiography if the noninvasive work-up was inconclusive. RESULTS: The prevalence of pulmonary embolism increased progressively, from 12% in patients <40 years of age to 44% in those ≥80 years of age. The positive predictive value of a high clinical probability of pulmonary embolism was greater in the elderly (71% to 78% in those ≥60 years old versus 40% to 64% in those ≤59 years old). The sensitivity of D-dimer testing was 100% in all age groups, but its specificity decreased markedly with age, from 67% in those ≤40 years old to 10% in those ≥80 years old. The diagnostic yield of lower limb compression ultrasonography was greater in the elderly. The proportion of lung scans that were diagnostic (normal, near-normal, or high probability) decreased from 68% to 42% with increasing age. CONCLUSIONS: Age affects the performance of common diagnostic tests for pulmonary embolism and should be kept in mind when evaluating patients suspected of having this condition.