[Benefit of direct determination of LDL-cholesterol (comparison with LDL measurement using calculated estimates]

Treatment of dyslipidemia and its frequently associated complications (manifest atherosclerosis) is very pretentious from the economic aspect. Diagnostic and therapeutic criteria are based mainly on biochemical analyses. Although demands on laboratories are relatively strict (respecting defined laboratory errors, analytical and preanalytical conditions), when defined diagnostic criteria are used, the results of biochemical analyses are not yet satisfactory. A typical example is the stratification of risk patients according to the LDL concentration which in our country is very often preferred, although the LDL concentration is based only on calculation (contrary to investigations from which the majority of recommendations was derived where the LDL concentration was assessed directly). We know from our own experience that a large percentage of results of estimated and assessed LDL differs significantly. Therefore we wanted to know whether the assessed LDL concentration correlates with its estimate according to Friedewald s formula and which analytes have the greatest impact on the LDL concentration. Our objective was also to assess th percentage of incorrectly listed patients (according to the LDL stratification scale). In 1997-1998 we examined a group of 4578 probands, patients of the consultant out-patient departments of the Sternberk hospital. Their mean age was 56 years. On average subjects with as slightly atherogenic phenotype were involved (classification A according to EAS). The values of lipid parameters did not differ significantly in the two sexes. The cholesterol, LDL and triacylglycerol concentrations increased with advancing age. The LDL values obtained by assessment and calculation correlated closely. The LDL value was influenced most by ApoB and total cholesterol. Triacylglycerols correlated with LDL assessment only up to a concentration of .3 mmol/l. HDL, ApoA-1 and higher triacylglycerol concentrations (1.3 mmol/l) did not correlate with the LDL value. The authors provided evidence that in subjects where it was possible to calculate LDL lege artis (2458 probands) were listed according to LDL calculation into a wrong group (stratification according to NCEP) whereby up to an LDL concentration .11 mmol/l this parameter cannot be predicted at all by calculation (error up to 85%). A satisfactory estimate is assumed only at LDL concentrations 5.2 mmol/l. Because the estimated LDL values are in the majority of patients lower than the calculated values, it may be assumed that during stratification of LDL obtained by calculation the patients are treated too aggressively. Assuming pharmacological treatment of all mentioned patients, it may be estimated that by using analyses of direct LDL for stratification of probands the costs of hypolipidaemic treatment will by reduced by about 1/4-1/3 (in the catchment area of the Sternberk hospital this would save more than 10 million crowns). The costs of LDL analyses per year are about 180,000 crowns (in the Sternberk hospital--which amounts to cca 1.5% of the money saved on pharmacotherapy).