Should liver function tests be included in definitions of metabolic syndrome? Evidence from the association between liver function tests, components of metabolic syndrome and prevalent cardiovascular disease
AIMS: The definition of metabolic syndrome (MS) continues to be debated and does not include abnormal liver function tests (LFTs). This study aims to determine: (1) the association between the five ATP3 MS diagnostic components and different LFTs, and (2) the association between raised LFTs and prevalent cardiovascular disease (CVD). METHODS: A total of 1357 patients, without alcoholism or known liver disease, from randomly selected households from rural Victoria, Australia, attended for biomedical assessment. Receiver operating characteristic (ROC) areas under the curve (AUC) were determined for associations between the ATP3 diagnostic components, and between LFTs and ATP3 diagnostic components. RESULTS: The range of ROC AUC for ATP3 diagnostic components was 0.60-0.77. Waist had the strongest association and blood pressure the weakest. The strength of association between ATP3 diagnostic components and gamma GT (GGT) was similar (0.63-0.72), but was less for alanine transaminase and aspartate transaminase. Using the ROC-derived GGT cut-off (men 27 IU, women 20 IU), those with MS and a high GGT had more CVD than those with MS and a low GGT, and those without MS (18% vs. 10% vs. 7%, respectively; P < 0.001). Among those with MS, after adjusting for covariates, the odds ratio of CVD was 2.66 (1.18-5.96) for a high GGT compared to a low GGT. CVD was not significantly more prevalent in MS patients with a low GGT compared to non-MS patients. CONCLUSIONS: We suggest that including a raised GGT in the criteria for MS could increase its predictive nature for CVD. Prospective studies are needed to confirm this finding.