How many components for the metabolic syndrome? Results of exploratory factor analysis in the FIBAR study

Abstract

Background and aims Factor analysis can be used as a basis for the determination of diagnostic criteria for the metabolic syndrome (MS). This approach can be used as a basis for the determination of diagnostic criteria for MS. Methods and results Exploratory factor analysis of Adult Treatment Panel (ATP)-III and International Diabetes Federation (IDF) criteria for MS, entered as dichotomic variables, was performed on 2945 patients enrolled in a screening programme for diabetes. The ability of calculated factors to identify patients with MS-related conditions (glucose intolerance, hyperuricaemia, and elevation of alanine aminotransferase; ALT) was assessed through Receiver Operator Characteristics (ROC) curve analysis. Alternative sets of criteria based on ATP-III and IDF definitions of MS were also assessed. A two-factor structure was found for both ATP-III and IDF criteria. Factor 1 (associated with fasting hyperglycaemia, hypertension, and elevated waist circumference) was capable of identifying subjects with MS-related conditions to a greater extent than factor 2 (low HDL-cholesterol and hypertriglyceridaemia). When a composite variable (low HDL-cholesterol and/or hypertriglyceridaemia) was used for dislipidaemia, a single factor structure was obtained both for ATP-III and IDF definitions; this factor structure was retained when hyperuricaemia was added as a fifth component of MS. Such a modified definition of MS was not inferior to original ATP-III and IDF criteria in the identification of subjects with glucose intolerance and elevated ALT. Conclusions A modification of current ATP-III or IDF criteria is necessary in order to obtain a single-factor structure. Alternative definitions of MS, including additional features, such as hyperuricaemia, can maintain a monofactorial structure, and an association with related conditions not inferior to that of original criteria.