[Methods of cholesterol determination: conventional procedure or "dry chemistry"?]

The search for the cardiovascular risk factor cholesterol should essentially be done in the physicians' laboratory. The majority of such analyses is performed by 'dry' chemistry tests. This review compares this technique with conventional methods for the determination of cholesterol. The reagents and the reaction mechanisms are principally the same for both techniques, i.e. fully enzymatic methods are used. In 'dry' chemistry the reagents are fixed on a solid carrier. The reactive state is provided by the liquid of the specimen. Two principles are employed: the technique of strips which is already utilised in urinary analysis and the system of multiple film layers as it is common in color-film technique. Three already introduced systems are discussed: the Seralyzer (Ames), the Ektachem (Kodak), and the Reflotron (Boehringer, Mannheim), and one system which is still in evaluation (the Clinistat, Ames). All the systems give a good agreement provided that they are operated by well-trained operators. Problems arise with quality control, since matrix effects are particularly important. The exactitude of the results depends on the calibration. Both, the Reflotron and the Clinistat are calibrated by the manufactories himself, the employer has no influence and is entirely dependent on the reliability of the producer. Although clinical chemistry analyses are facilitated by 'dry' chemistry it is by no means devoid of risks because the errors are more difficult to recognize.