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PP64 Developing self-reported classifications of metabolic syndrome for use in epidemiological research: how well might they reflect clinical diagnoses of metabolic syndrome?
  1. R Alfawaz,
  2. EM Scott,
  3. GR Law,
  4. GTH Ellison
  1. Temporal Influences on Metabolic Events (TIME) Research Group, Leeds Institute of Genetics, Health and Therapeutics, University of Leeds, Leeds, UK

Abstract

Background Traditional classifications of the metabolic syndrome (MetS) rely on measurements of central obesity and clinical diagnoses of diabetes, hypercholesterolaemia and hypertension – criteria that are rarely available in large-scale epidemiological surveys. The aim of the present analysis was to assess whether questionnaire-derived, self-reported information on clinical diagnoses might offer a valid assessment of MetS in populations with good access to health care and health surveillance.

Methods The analyses used data from Understanding Society’s (USoc) Wave 2 Health Assessment – a subsample of n = 6853 men and n = 8793 women, with a mean (SD) age of 50.5 (17.8) years that included data collated from previous questionnaires with measurements taken during home visits by trained research nurses. These were used to generate self-reported and objectively-assessed classifications of MetS. ‘Central obesity’ (CO) was defined as participants: who were obese (body mass index 30 kg/m²); and whose waist circumference exceeded WHO cut-offs (102 cm for men; 88 cm for women). Objective measurements of blood pressure exceeding NICE hypertension severity stage 2 cut-offs (Systolic blood pressure (SBP) 160 mm Hg; Diastolic blood pressure (DBP) 100 mm Hg), with/without prescribed antihypertensive medication, were used to classify ‘observed hypertension’ (O-HBP). Participant-reported clinical diagnoses of hypertension were used to classify ‘self-reported hypertension’ (SR-HBP). ‘Objective Hypertensive MetS’ (O-HBPMetS) was defined as CO plus O-HBP; ‘Self-reported MetS’ (SR-HBPMetS) was defined as CO plus SR-HBP.

Results Over a quarter of participants (28.7%) were obese and almost half (44.2%) exceeded waist circumference cut-offs; women being more likely to have obesity (57.5%) or CO (59.0%) than men (42.5% and 41.0%, respectively). While 21.8% had a self-reported clinical diagnosis of hypertension, only 8.9% had been prescribed hypertensive medication and/or had SBP/DBP readings that met NICE stage 2 severity levels. Unsurprisingly, substantially more participants were estimated to have SR-HBPMetS (8.7%) than O-HBPMetS (3.5%), such that the sensitivity and specificity of SR-HBPMetS for O-HBPMetS was 81% and 94%, respectively. And while the negative predictive value of SR-HBPMetS was 99% its positive predictive value was just 32%.

Conclusion These findings indicate that substantially more participants recall a clinical diagnosis of hypertension than those with NICE stage 2 severity hypertension and/or prescribed antihypertensive medication – suggesting that clinicians diagnose and/or treat hypertension at lower blood pressure levels than those recommended by NICE. For this reason SR-HBPMetS provides a less conservative assessment of MetS than O-HBPMetS when the latter are based on NICE severity criteria. Context-specific sensitivity analyses are therefore required to optimise the utility of SR-HBPMetS as a measure of O-HBPMetS in epidemiological surveys.

Keywords
  • metabolic syndrome
  • diagnosis
  • self report

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