Clinical laboratory parameters in osteoarthritic knee-joint effusions correlated to trace element concentrations

Interactions of clinical laboratory parameters with trace elements in knee- joint effusions might turn out to be potential diagnostic tool, increasing our pathophysiological understanding and knowledge on knee-joint effusions. Thus, the 11 clinical laboratory parameters, total protein, albumin, gluco se, lactate dehydrogenase, uric acid, pH, rheumatoid factor, antistreptolys in, C-reactive protein, leukocyte, and erythrocyte counts were determined i n 39 osteoarthritic knee-joint effusions and in corresponding sera. Additio nally, concentrations of the 17 trace elements barium, beryllium, calcium, cadmium, cesium, copper, lanthanum, lithium, magnesium, molybdenum, lead, r ubidium, antimony, tin, strontium, thallium, and zinc in both effusions and corresponding sera were quantified by inductively coupled plasma-mass spec trometry. Concentrations of most laboratory parameters in synovial fluid we re within the normal ranges for serum. However, concentrations of total pro tein and albumin in effusions were distinctly lower than in sera of healthy adults. Results for rheumatoid factor, antistreptolysin, and C-reactive pr otein in the effusions were below their corresponding threshold values for serum. An indicator for inflammation, the leukocyte count had a median < 6. 3 G/L. The erythrocyte count (median: < 0.06 T/L) revealed a very low prese nce of red blood cells in the effusions. Total protein concentrations and l actate dehydrogenase activity in the effusions correlated positively with e ffusion copper (r = 0.61 and 0.66) and effusion zinc (r = 0.71 and 0.49). F or cesium, a negative correlation in both sera (r = -0.44) and effusions (r = -0.44) with LDH activity could be established. Concentrations of rubidiu m, strontium, and cesium responded to albumin concentrations in sera and in effusions, establishing an inverse correlation. All other trace elements s howed no or only weak associations with the clinical laboratory parameters determined. Although distinct relationships between trace element concentra tions and clinical laboratory parameters in knee-joint effusions exist, the clinical relevance of these findings needs to be further elucidated.