What Are the Determinants of Insulin Resistance (IR) and How Effective Is the Sub-Saharan Africa-Specific Threshold of Abdominal Obesity (AO-SSA) Identifying IR in Congolese Black Hypertensive Patients?

Abstract

Background: Hypertensive patients with insulin resistance (IR) are at greater risk of cardiovascular disease and may represent a particular subset of hypertension (HTN) requiring special medical attention. Quantitative measurements of the IR are not suitable for routine clinical practice. Metabolic syndrome (MetS) or simply abdominal obesity (AO) is surrogate of IR. The performance of the recently proposed Sub-Saharan Africa cutoff point of abdominal obesity for identifying IR in hypertensive patients has never been evaluated. Aims: The main objective was to compare the performance of the newly proposed Sub-Saharan Africa specific threshold of abdominal obesity (AO-SSA) to that of IDF (AO-IDF) in identifying IR in Congolese Black Hypertensive Patients. Methods: A cross-sectional study was conducted at the Heart of Africa Cardiovascular Center, Lomo Medical Clinic, Kinshasa Limete, DR Congo, between January 2007 and January 2010. Homeostatic model assessment (HOMA) index was calculated to determine IR. Multivariate logistic regression analysis was used to assess the independent determinants of IR. The intrinsic (sensitivity and spe-* Corresponding author. B. Kianu Phanzu et al. 643 cificity) and extrinsic (positive predictive value and negative predictive value) characteristics of the AO-SSA, AO-IDF, AO-ATP III, MetS-SSA, MetS-IDF, and MetS-ATP III were calculated. The kappa statistic was determined for agreement between the ATPIII, IDF and SSA defined AO and MetS with HOMA-IR. Results: Men represented the majority of the enrolled patients: 105 (64.4%) and the mean age of all participants were 57 ± 11 years. Insulin resistance was found in 79.1% of the study population with 88.7, 79.3, 84.6, 71.4, 75.5, 91.1, 60.3 and 44.8 respectively among patient with MetS-ATP, MetS-IDF, MetS-SSA, AO-ATP III, AO-IDF, AO-SSA, diabetics and non-obese non-diabetic hypertensive patients. In multivariate analysis, the risk of IR was associated independently and significantly (p < 0.05) with cigarette smoking, low-HDL-C, hyperuricemia, and diastolic HTN, as shown in the following equation: Y = −1.404 + 1.054 Cigarette Smoking + 0.872 low HDL-C + 0.983 hyperuricemia + 0.852 diastolic hypertension. The AO-SSA, with 87.7% sensitivity and 67.6% specificity, was the only surrogate who showed an acceptable agreement with the HOMA-IR index. Abdominal obesity defined according to other thresholds and the metabolic syndrome whatever the used diagnostic criteria have a slight agreement with the HOMA-IR index. Conclusion: IR was found to be prevalent in our study population. Cigarette smoking, low-HDL-C, hyperuricemia, and isolated diastolic HTN magnify IR. The AO-SSA is an easy and cost efficient method to diagnose IR in Congolese Black Hypertensive Patients. Further study in wider group is indicated to validate our findings.