Low sensitivity of plasma DNA in screening for pulmonary embolism

Detection of plasma deoxyribonucleic acid (DNA) by counterimmunoelectrophoresis (CIE) has been proposed as a rapid, inexpensive screening test for the diagnosis of pulmonary embolism (PE). To test the sensitivity of plasma DNA detection for the diagnosis of PE, we obtained blood samples from 89 patients when they underwent lung scanning for suspected PE. Plasma was analyzed qualitatively for DNA by CIE, using antiserum that could detect as little as 0.2 micrograms DNA/ml. Among 16 patients with PE diagnosed by high probability lung scan, pulmonary angiography, or at autopsy, plasma DNA was detected in 3 patients--a sensitivity of 19%. Of 6 patients with indeterminate lung scans and a possible diagnosis of PE, 1 had detectable plasma DNA. None of the 67 patients without a diagnosis of PE had detectable plasma DNA, so the specificity was 100%. Thus, although detection of plasma DNA by CIE has many desirable features of a screening test, further studies are needed before this test can be recommended in routine screening for PE.