Comparison between D-Dimer levels and lung scan in patients with suspected pulmonary embolism

Pulmonary embolism (PE) is a critical situation that requires prompt diagnosis and treatment. Lately, the use of D-Dimer (DD) blood level test was recommended when PE is suspected. The goal of this work was to evaluate the association between DD levels and the results of lung scan in patients with suspected PE. 84 patients who were admitted due to suspected PE and met the inclusion criteria of having both DD test and lung scan within less than 7 days apart, were included in our study (age = 76 ±14, females = 58, males = 26). Comparison of lung scan results, DD level and diagnosis of PE at discharge was carried out. The subjects were classified into 2 groups according to the DD levels: group A = DD= >250 ng/mL - abnormal test, group B = DD < 250 ng/mL - normal test. Group A includes 67 patients, of which 29 (43%) were diagnosed as PE. In these subgroup lung scan showed high Probability (HP) for PE in 19 (66%), medium probability (MP) in 9 (31%) and low probability (LP) in 1 (3%). From the 38 (57%) patients who were not diagnosed with PE (non-PE), 5 (13%) had HP lung scan, 4 (11%) MP and 29 (76%) LP. Group B includes 17 patients, in which only one (6%) had diagnosed with PE and the rest (n = 16, 94%) had no PE. Of the latter subgroup 15 (94%) had LP lung scan and one MP scan. The one patient who was diagnosed with PE had a HP lung scan that was also confirmed with CT-angiography. DD and lung scan had similar sensitivity (96.7%) and high negative predictive value (NPV = 94.1% and 97.8% accordingly) for PE. On the other hand DD specificity is much lower (29.6%) in comparison to lung scan (81.5%). The results of this work support the use of DD test prior to lung scan, in order to rule out PE with relatively high probability.