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Background: Many different multiplex biomarker immunoassays based on Luminex®-technology have been developed during recent years. We have evaluated the performance of two multiplex immunoassays for determination of adiponectin, resistin, ghrelin and leptin in comparison to corresponding, conventional ELISA assays., Methods: Human serum or plasma samples were analysed by commercially available multiplex and ELISA immunoassays manufactured by Millipore Corp., Results: The correlation between tested multiplex and ELISA immunoassays was good, r > 0.9 for all analytes. The agreement between the methods was acceptable but there were differences in analytical levels. Intra- and inter-assay variation was comparable between both assays. The coefficient of variation for all analytes, independent of method, was ≤15% and for most of them <10%., Conclusion: The performance of the tested multiplex assays was reasonable and they can be considered as valid options to the conventional ELISA assays. However, results obtained with the two different techniques are not necessarily interchangeable due to differences in the concentration levels.

The lipoprotein components were studied in connection with a population study concerning the state of health and living habits of the elderly people in Turku, Finland. Serum levels of total cholesterol, high density lipoprotein (HDL) cholesterol, triglycerides, apolipoprotein A1 (apo A1) and apolipoprotein B (apo B) of the 347 elderly people (aged 65 years or over) were measured and those of low density lipoprotein (LDL) cholesterol were calculated. The levels of total cholesterol, LDL cholesterol and apo B were significantly higher in females than in males, and the concentrations decreased with advancing age. The concentrations of HDL cholesterol and apo A1 were significantly higher in females than in males but age had no effect. Serum triglycerides behaved differently in males and females; in females age had a significant increasing effect whereas in males no age effect was observed. The apo A1/apo B ratio did not differ between males and females. Reference values of serum lipids, lipoproteins and apolipoproteins of the elderly are suggested.

Rapid immunochemical assays were developed for the determination of apolipoproteins A-1 and B in serum. The methods are based on the measurement of immunoprecipitation at a wavelength of 340 nm. Both assays are easy to perform, their reproducibilities are good (the coefficients of variation for within-run and between-run imprecisions are below 5%), and their correlations with radial immunodiffusion method are high (r = 0.96). The effect of storage on native serum specimens was also studied. Apolipoprotein B is stable at least 4 weeks in a refrigerator but in some specimens the level of apolipoprotein A-1 rises nearly 10% during this time. Repeated freezing and thawing, on the other hand, may have a harmful effect, especially on apolipoprotein B. Therefore, use of fresh serum specimens is recommended for both assays. The present method is well suited for routine measurements because it can be easily adapted to most clinical chemistry analysers.

Serum lipid levels were followed in myocardial infarction patients for one year after the infarction and related to their drug use and physical performance. Serum triglyceride concentrations were significantly elevated in patients using diuretics or diuretics and beta-blockers together both 3 and 12 months after the infarction when compared to patients not having drugs. The beta-blockers alone did not change triglycerides. No differences were found in total cholesterol concentration between any of the drug groups. The HDL cholesterol levels were significantly lower in all the drug groups 12 months after the infarction in comparison with the group using no drugs, but 3 months after the infarction these differences were not present. Total work in the exercise stress test correlated negatively with serum triglycerides and total cholesterol and positively with HDL/total cholesterol ratio in the group using no drugs 12 months after the infarction. In beta-blocker users, total work correlated negatively with triglyceride and total cholesterol concentrations. In all drug groups no correlation between total work and HDL/total cholesterol ratio could be found. These data suggest that despite differences in the physical working capacity between the groups, the drugs themselves are major determinants of differences in serum lipids.