Portable Cholesterol Analyzers

To the Editor.— Naughton et al¹ concluded that portable cholesterol analyzers at three of four sites had insufficient accuracy, resulting in a high percentage of misclassified patients (mostly false negatives). However, the study has a number of flaws and omissions that may invalidate their results. A significant problem is the effect of posture on blood cholesterol measurements. Blood cholesterol concentrations fall significantly when an ambulatory patient sits or lies supine.^2,3 The National Cholesterol Education Program Expert Panel recommends that patients be seated for at least 5 minutes before blood is drawn.⁴ The authors do not describe any attempt at minimizing the effects of postural changes. In their study, venous samples were obtained after finger-stick samples. If the patients were seated prior to their finger-stick cholesterol determination and were ambulatory prior to venipuncture, then the venipuncture cholesterol levels would be higher than those obtained by finger stick because