['The ratio of apolipoprotein B (apoB) to apolipoprotein A1 (apoA1) has been reported to be associated with metabolic syndrome (MetS) and insulin resistance (IR). Non-HDL-C is regarded as a surrogate marker for apoB in routine clinical practice. However, it is unclear whether the ratio of non-HDL-C to HDL-C is an equal or a better predictor than the apoB/apoA1 ratio for the identification of MetS and IR.', 'We performed a retrospective study of 41,821 Korean adults who participated in a routine health screening examination. Anthropometry, fasting glucose, fasting insulin, HOMA-IR, CRP, lipid profiles, apoB, and apoA1 were measured.', 'To compare the predictive value for MetS between different lipid ratios, we analyzed the ROC curves of apoB/apoA1 and non-HDL-C/HDL-C ratios. ROC analysis showed that the AUCs of non-HDL-C/HDL-C (0.75 [95% CI=0.74-0.76] in men and 0.84 [95% CI=0.83-0.85] in women) were significantly higher than those of apoB/apoA1 (0.66 [95% CI=0.65-0.67] in men and 0.77 [95% CI=0.76-0.78] in women). The non-HDL-C/HDL-C ratio also showed a significantly stronger association with HOMA-IR than the apoB/apoA1 ratio. The optimal cutoff value of the non-HDL-C/HDL-C ratio for detection of MetS in men was 3.39, with a sensitivity of 66.7% and a specificity of 71.8%, whereas the optimal ratio cutoff value in women was 2.89, with a sensitivity of 75.7% and a specificity of 78.1%.'] Is non-HDL-cholesterol/HDL-cholesterol a better predictor of metabolic syndrome and insulin resistance than apolipoprotein B/apolipoprotein A1?