Specificity of vessel criteria for pulmonary hypertension too low for clinical use

While the sensitivity of vessel criteria for identifying patients with pulmonary hypertension offers high sensitivity, the specificity may be too low for routine use in a clinical patient population, according to a study published in the April issue of Academic Radiology.

Pulmonary hypertension is difficult to diagnose early and noninvasively, though rule-based criteria have been previously created to diagnosis it on the basis of vessel measurements on CT scans. These criteria include the main pulmonary artery diameter (MPAD) and ratio of the MPAD to the diameter of the aorta (rPA) at the level of bifurcation of the main pulmonary artery, according to lead author Neal Corson, PhD, of the University of Chicago, and colleagues. They sought to examine the sensitivity and specificity of the established rule-based criteria. They also investigated the correlation between image-based MPA, rPA and catheterization measurements and aimed to establish the discriminatory capability of pulmonary artery measurements in differentiating patients with pulmonary hypertension from “normal” patients with the condition’s current clinical definition.

The study included data from 191 patients, of which 175 were diagnosed with pulmonary hypertension. The criteria used by the researchers stated that MPAD was greater than 29 mm for patients with the condition, and rPA was greater than one. Results indicated that the sensitivity and specificity in patients with pulmonary hypertension, based on the criterion that MPAD is greater than 29 millimeters, were 0.89 and 0.83, respectively. The sensitivity and specificity of the criterion that rPA is greater than one were 0.89 and 0.82, respectively.

When patients with pulmonary hypertension and “normal” patients were separated, the specificity was 0.95. The sensitivity of MPAD was 0.81, and the sensitivity of rPA was 0.76. Interestingly, the specificity for both decreased when patients without the condition were included.

“When applied to the patient cohort in this study, previous rule-based vessel-measurement criteria for PH diagnosis have a specificity that may be too low in a clinical setting to identify patients for further PH workup, namely because of the low prevalence of PH,” according to Corson and colleagues. “A future prospective study that specifically targets patients who undergo CT scanning for relevant indications must be conducted.”