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The analytical variation of immunoassays is at present significantly larger than that of other methods in clinical chemistry. The main sources of this large variation are variation between methods, lot to lot variation, and the large imprecision between-runs and within-runs when the methods are not performed on automated instruments. The variation can be substantially reduced by standardization, by ensuring the comparability between lots, and by automation of the analytical procedure. The extent to which the variation should be reduced is determined by the needs of medical decision making. It is demonstrated using the analytes TSH and CA 15-3 as examples that quality requirements have to be individually specified for each analyte. Such guidelines should be established by teams of international experts. They should include suggestions for reference methods, guidelines on the extent of comparability between routine methods, the maximum allowable deviations from lot to lot, and the minimum requirements for between-run precision. Such guidelines could form the basis for improvements which are directed towards the medical requirements.

3 derivatives 2g--i of 6-(4-diethylamino-1-methylbutylamino)-4-methoxy-2-methylquinoline and 6 derivatives 2k--p of 6-(4-diethylamino-1-methylbutylamino)-2,4-dimethylquinoline were synthesized with variations of substituents in positions 5 and 8 (--H, --OH, --OCH3, --CH3, --Cl) with the aim of studying the influence of these substituents, which facilitate, complicate or prevent oxidation to o- and (or) p-quinones, on antimalarial activity and toxicity. One methoxy group is necessary for activity against Plasmodium vinckei in position 5 or 8, no substituent that prevents oxidation is allowed in para position to this methoxy group.

On the basis of examinations of altogether 197 patients the results of the changes of GOT and GPT were compared with the old and new colour tests of the AWD Dresden in normal histology, virus hepatitis, fatty liver, liver cirrhosis and posthepatic occlusion. Though the new colour test reveals a higher sensitivity, the differential diagnosis between selected liver diseases, especially virus hepatitis and posthepatic occlusion syndrome have become more difficult. The cause for this is the less significant separability between the individual regions of reference.

The effects of oral contraceptives on the average biological intra-individual variation of 22 clinical-biochemical analytes were investigated. There was no effect for sodium, chloride, potassium, calcium, urea, creatinine, uric acid, HDL-cholesterol, triglycerides, thyroxin, triiodothyronine, ASAT, ALAT, gamma-GT, AAP, ChE in serum. Whereas the average biological intra-individual variation of total protein, albumin, cholesterol, hemoglobin and amylase were significantly higher in the group of women taking oral contraceptives. For these analytes the use of oral contraceptives must be considered in establishing decision making criteria for longitudinal monitoring.

The diagnostic validity of multivariate combinations of alpha 1-antitrypsin, alpha 2-macroglobulin, C-reactive protein, complement C3, complement C4, neopterin in serum, and neopterin in urine as markers for acute cardiac allograft rejection and for differential diagnosis of rejection and infections was investigated in the follow-up of 37 patients with heart transplants. Rejection was diagnosed by endomyocardial biopsy. Infections were classified as 'no infection', 'viral infection', and 'bacterial, fungal or mixed infections'. Although there are significant differences between the mean levels of analytes, multivariate discriminant analysis does not provide an adequate discrimination of rejection and infection states. In separate rejection diagnosis, multivariate combinations of analytes cannot replace endomyocardial biopsy. However, a multivariate combination of alpha 1-antitrypsin, alpha 2-macroglobulin, C-reactive protein, C3, C4 in serum, and neopterin in urine can be used as a screening procedure to reduce the number of endomyocardial biopsies.

The optimal utilization of the knowledge and possibilities of pathological and clinical biochemistry presumes a close cooperation between it and the clinical specialties. The common working team of the GDR Society of Internal Medicine and the GDR Society for Clinical Chemistry and Laboratory Diagnostics makes theses of the central points of the cooperation in care, education, further education and postgraduate study and in research a subject for discussion. As essential tasks in the process of medical care are regarded the balance of the examination programme standing at the disposal, the establishment of diagnostic programmes, the establishment of organisational measures, the ascertainment of a use according to indication, the guarantee of the representance of examination material, the control of plausibility and the interpretation of test results. Since the realization of the tasks to a large extent depends on the cooperation of the specialities in education, further education and postgraduate study during the further education the clinician should become acquainted with the possibilities, the limits and the prerequisites for the performance of laboratory diagnostic investigations, the clinical biochemist with the problems of medical care and the value of the laboratory diagnosis in the total process of the treatment. In the field of research the result is a necessary cooperation in the clarification of patho-biochemical mechanisms, in the search for suitable laboratory diagnostic parameters for diagnostics and control of the course as well as in the statement of the validity of laboratory diagnostic parameters and parameter combinations taking into consideration the factors expenses, benefit and risk as well as further diagnostic possibilities.

The usability of the new and old standardized colour test for the determination of the aspartate aminotransferase (GOT) (set of test instruments VEB Arzneimittelwerk Dresden) in the differential diagnosis between acute myocardial infarction and angina pectoris are compared. Concerning this problematics the new colour test does not evoke a better separation effect than the old one. Since with the change-over there were connected considerable uncertainties in the clinic it is recommended in case of a future standardisation to publish the regions of reference and first clinical experiences before the change-over.