Atherogenic index of plasma: a useful marker for subclinical atherosclerosis in ankylosing spondylitis

Ankylosing spondylitis (AS) is associated with an increased risk of atherosclerotic cardiovascular disease (ACD). The atherogenic index of plasma (AIP), which is the logarithmic transformation of the plasma triglyceride (TG) level to the high-density lipoprotein level (HDL) ratio, has been suggested to be a novel marker in the identification of atherosclerosis risk. Therefore, this study aims to determine if the AIP can act as an accurate marker for the detection of subclinical atherosclerosis. Fifty-two male patients with AS and 52 age-, gender-, and body mass index (BMI)-matched healthy control subjects were included in the study. For each patient, AIP and total cholesterol (TC)/HDL values were calculated and carotid artery intima-media thickness (cIMT) was measured. The mean (SD) cIMT and median (range) AIP values for AS patients were higher than that of the healthy control subjects (0.60 ± 0.18 vs. 0.51 ± 0.10, p = 0.003 and 0.23 [− 0.32 to 0.85] vs. 0.09 [− 0.53 to 0.49], p = 0.007, respectively). A positive correlation was found between the patients’ cIMT and AIP values (r = 0.307, p = 0.002) and TC/HDL values (r = 0.241, p = 0.014). Regression analysis revealed an independent association between the subclinical atherosclerosis and AIP (beta [β] = 0.309, p = 0.002). There were no independent correlations between subclinical atherosclerosis and TC (β = 0.245, p = 0.065), TG (β = 0.185, p = 0.515), HDL (β = 0.198, p = 0.231), TC/HDL (β = 0.032, p = 0.862), and low-density lipoprotein (LDL) (β = 0.151, p = 0.246). A strong and independent correlation exists between AIP and cIMT values. Therefore, the AIP could serve as a better marker than the TC/HDL ratio for the detection of subclinical atherosclerosis in AS patients.