Does simplified Well’s score combined with age-adjusted d-dimer reduce inappropriate CT pulmonary angiogram and incidence of contrast induced nephropathy?

Background: Pre-test probability testing is essential for diagnosis of pulmonary embolism (PE) and to limit undue CT pulmonary angiogram (CTPA). There is limited data on combination of Simplified Well’s score (SWS) with age-adjusted d-dimer (AAD). Aim: To determine impact of SWS and AAD on appropriateness of CTPA and incidence of contrast induced nephropathy (CIN). Methods: Retrospective analysis of consecutive patients undergoing CTPA at University Hospitals of North Midlands from 01/05/2017 – 31/08/2017. SWS and AAD were calculated retrospectively to compare their performance with original Well’s score (OWS) and d-dimer. CIN was defined as per Guidelines(KDIGO). Results: 310 patients had CTPA during the specified period of which 83 (26.7%) had PE. D-dimer had a sensitivity of 97.1%, specificity 17.9% and negative predictive value (NPV) 93.7%. The proportion of confirmed PE were 8/62 (12.9%) in low, 35/215 (30.2%) in intermediate and 10/33 (30.3%) in high probability of three-level OWS. AAD calculated on patients >50 years of age (n=198) had sensitivity of 86.5%, specificity 61% and NPV 86.9%. The proportion of confirmed PE patients were 12/114 (10.5%) in PE unlikely and 72/196 (36.7%) in PE likely category of SWS. AAD increased the specificity of d-dimer significantly and 53 CTPA (17.1%) could have been avoided by using AAD cut-off. 18 patients (5.8%) developed CIN, of which 2 (11.1%) could have been prevented by using the AAD cut-off. Conclusion: OWS and SWS have comparable performance but SWS is preferable due to its practicality. AAD improves the specificity while retaining sensitivity of d-dimer and prevents inappropriate CTPA and CIN.