Laboratory Evaluation of the Obese Patient
Although one could make a case for obtaining a large number of biochemical tests in the evaluation of an obese patient, a more limited initial screen seems warranted. A fasting sample of blood for glucose; total, LDL, and HDL cholesterol; and triglyceride levels is clearly indicated. These tests, along with an appropriate history, will provide the information necessary for cardiovascular risk stratification and can be used to rule out diabetes or impaired fasting glucose (25,57). Some have advocated obtaining a glycosylated hemoglobin (HbA1C) level to screen for diabetes. Although this test should be useful in the diagnosis of diabetes, the assay method has not been standardized and at this time there is no widely accepted diagnostic criteria for diabetes based on an HbA1C level. In addition, some have advocated obtaining a fasting insulin level to determine whether insulin resistance is present. Unfortunately, here again, methods for assaying insulin have not been standardized and there are no widely accepted diagnostic criteria for diagnosing insulin resistance based on an insulin level. Although metrics such as the homeostasis model assessment (HOMA) calculation, which use the fasting insulin and glucose levels, have a greater ability to estimate insulin action, the same problem with nonstandardized insulin assays apply, so this approach is not yet appropriate for general clinical use. In fact, the waist circumference and fasting triglyceride and glucose levels give almost as much information about insulin action as a HOMA calculation (58). A plasma measure of high high-sensitivity C-reactive protein (hsCRP) appears to also provide useful information in risk-stratifying patients for cardiovascular disease (CVD) risk (59). It is increasingly becoming clear that inflammation plays an important role in CVD risk, and the level of hsCRP provides an indication of the degree of inflammation present in an individual patient (60). Statin therapy has been shown to reduce hsCRP levels, and CVD outcomes correlate with the degree of hsCRP achieved following statin therapy (61,62). However, the exact role of measuring hsCRP levels in overall CVD risk management remains undefined at this time.