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Zusammenfassung Osteoporose wird von der WHO zu den ökonomisch bedeutsamsten Erkrankungen des 21. Jahrhunderts gezählt. Abgesehen von Anamnese, klinischer Untersuchung und bildgebenden Verfahren sind Laboruntersuchungen wichtige Werkzeuge in der Diagnose, Therapieüberwachung und Verlaufskontrolle der Osteoporose. Man unterscheidet Basis-Laboruntersuchungen von weiterführenden Laboruntersuchungen. Das Basislabor dient zur Differentialdiagnose zwischen primären und sekundären Formen der Osteoporose. Ursachen der sekundären Formen der Osteoporose müssen unter anderem durch weiterführende Untersuchungen abgeklärt werden. Spezielle Biomarker des Knochenstoffwechsels werden hauptsächlich zur Therapieüberwachung und Verlaufsbeurteilung der Osteoporose genutzt.

Summary: Efficacy data as well as correlations of test results measured by different automated immunoassay analysers are obligatory for organisational and medical decisions on a rational scientific basis. Thus, we compared the serum concentrations of reproductive hormones (lutropin, follitropin, estradiol, progesterone, testosterone and prolactin) measured by automated immunoassay-procedures performed on ARCHITECT (Abbot-Laboratories, USA), Elecsys 2010 (Roche-Diagnostics, Switzerland) and IMMULITE 2000 (Diagnostic Products Corporation, USA). Similarly, concentrations of hormones for the estimation of thyroid function (thyreotropin, thyroxin, free thyroxin, triiodothyronine and free triiodothyronine) were measured by these analysers and in addition by AxSYM (Abbot-Laboratories, USA) and ACS:Centaur (Bayer, Germany). At low hormone concentrations we observed for all investigated immunoassays a low day-to-day precision, which might be clinically relevant especially for testosterone and estradiol measurements in women and children. The different assays for reproduction-hormones generally showed a high correlation, whereby a higher scattering of data around the regression lines was observed in the lower measuring range. However, IMMULITE 2000 measured higher testosterone concentrations than the other methods. Differences between results obtained by diverse lutropin and prolactin assays were apparently due to different test calibrations. Most automated thyroid-hormone assays correlated quite well. Higher levels for free triiodothyronine were, however, measured by Elecsys 2010. Although results from the new generation of automated immunoassay-analysers showed some improvements regarding intermethod comparability, it seems still partly unavoidable to establish method specific reference ranges.

Background Macro-hormones are circulating conjugates of hormones with immunoglobulins, which often artefactually elevate biochemical test results. Particularly when causing only moderate elevation no suspicion will be raised. By far the most frequently encountered macro-hormone is macro-prolactin. Here we report a female patient with rheumatoid arthritis who had persistently and grossly elevated thyroid stimulating hormone (TSH) but normal free thyroxine in electrochemiluminescent assays. Although clinically euthyroid, she was put on thyroxine therapy which caused hyperthyroid symptoms. Methods An analytic interference by macro-TSH was assumed by dilution experiments, polyethylene-glycol-precipitation, the addition of a heterophilic antibody blocking reagent and size exclusion chromatography. Results Further workup, however, revealed the presence of anti-ruthenium antibodies. Conclusions To our knowledge this is the first report of anti-ruthenium antibodies selectively interfering with a TSH assay and causing erratic gross elevation of TSH mimicking macro-TSH.

The World Health Organization ranks osteoporosis as one of the economic most significant diseases of the 21st century. Apart from anamnesis, physical examination and imaging techniques, laboratory tests are important tools in the diagnosis and monitoring of osteoporosis. Basic laboratory tests can be distinguished from advanced laboratory tests. The basic laboratory tests are used to differentiate between the primary and secondary form of osteoporosis. Further laboratory tests can clarify the causation of secondary forms of osteoporosis. Biochemical markers of bone turnover are particularly used for monitoring the therapy and the course of osteoporosis.

We investigated the effects of hormone replacement therapy (n = 27) on biochemical markers of bone turnover in a cross-sectional study of 127 postmenopausal women (according to WHO guidelines 18 patients had normal bone mineral density and 109 suffered from bone loss). Urinary excretion of free deoxypyridinoline and C- or N-telopeptide fragments of type I collagen served as bone resorption markers, serum osteocalcin as a bone formation marker. In women with no hormone replacement therapy, only C- and N-telopeptides correlated significantly with the lumbal T-score as an index for bone mineral density. Patients with bone loss receiving hormone replacement therapy exhibited significantly lower C-telopeptide, N-telopeptide and osteocalcin levels than those with no therapy (mean -45%, -43% and -26%, respectively), while deoxypyridinoline showed no significant differences. Among the markers investigated, C- and N-telopeptides seemed to be more reliable to detect therapeutic effects on bone metabolism. We present a preliminary model to evaluate bone turnover and resorption/formation rate.