Prevalence of pulmonary arterial hypertension (PAH) by apolipoprotein quartiles. (A) Low apoA-I levels trend with high prevalence of PAH. The apoA-I levels from Figure 1 were grouped into the lowest, highest, and middle 2 quartiles, and the percentage of patients with TRV 2.5 m/s or higher was calculated. There is a strong trend toward higher prevalence of PAH in the lower apoA-I group in this analysis (P = .06, χ² test for trend). (B) A similar analysis for apoB shows the highest prevalence of PAH in the highest quartile of apoB levels (P = .05) and (C) even more strikingly, with high apoB/apoA-I ratio (P = .006).