Follicle-stimulating hormone and bioavailable estradiol are less important than weight and race in determining bone density in younger postmenopausal women.

UNLABELLED: The association between follicle-stimulating hormone (FSH) and bone density was tested in 111 postmenopausal women aged 50-64 years. In the multivariable analysis, weight and race were important determinants of bone mineral density. FSH, bioavailable estradiol, and other hormonal variables did not show statistically significant associations with bone density at any site. INTRODUCTION: FSH has been associated with bone density loss in animal models and longitudinal studies of women. Most of these analyses have not considered the effect of weight or race. METHODS: We tested the association between FSH and bone density in younger postmenopausal women, adjusting for patient-related factors. In 111 postmenopausal women aged 50-64 years, areal bone mineral density (BMD) was measured at the lumbar spine, femoral neck, total hip, and distal radius using dual-energy X-ray absorptiometry, and volumetric BMD was measured at the distal radius using peripheral quantitative computed tomography (pQCT). Height, weight, osteoporosis risk factors, and serum hormonal factors were assessed. RESULTS: FSH inversely correlated with weight, bioavailable estradiol, areal BMD at the lumbar spine and hip, and volumetric BMD at the ultradistal radius. In the multivariable analysis, no hormonal variable showed a statistically significant association with areal BMD at any site. Weight was independently associated with BMD at all central sites (p < 0.001), but not with BMD or pQCT measures at the distal radius. Race was independently associated with areal BMD at all sites (p ≤ 0.008) and with cortical area at the 33% distal radius (p = 0.004). CONCLUSIONS: Correlations between FSH and bioavailable estradiol and BMD did not persist after adjustment for weight and race in younger postmenopausal women. Weight and race were more important determinants of bone density and should be included in analyses of hormonal influences on bone.

The impact of hemolysis on Ortho-Clinical Diagnostic's ECi and Roche's elecsys immunoassay systems.

BACKGROUND: Hemolysis is regularly encountered in clinical specimens and often interferes with a variety of laboratory test methods. Although not widely recognized, immunoassays based on nonisotopic detection systems can also be affected by hemolysis. For this reason, we investigated the effect of differing amounts of hemolysis across a range of values for several immunoassays on the Ortho-Clinical Diagnostics ECi and Roche Elecsys platforms. METHODS: Hemolysate was prepared from whole blood and spiked at varying concentrations into pooled patient serum samples for different analytes. RESULTS: Out of the 21 analytes tested, six (28.6%) exhibited significant increases or decreases in measured concentrations with increasing amounts of hemolysis. CONCLUSIONS: Although immunoassays are generally thought to be impervious to hemolysis interference, hemolysis can interfere in immunoassay testing platforms. For these reasons, we recommend that laboratories conduct hemolysis interference studies for all laboratory test protocols.

Intoxication with nitromethane-containing fuels: don't be "fueled" by the creatinine.

BACKGROUND: This report describes two patients exposed to nitromethane-containing fuels and the resulting laboratory abnormalities. Patient 1 ingested model airplane fuel on two separate occasions; the second patient had dermal exposure from clothing saturated with fuel in a drag racing accident. After the exposure, both patients had unusually elevated serum creatinine concentrations. METHODS: We determined the cause of the increase in serum creatinine to be due to nitromethane interfering with the Jaffé reaction used to measure this analyte. The interference was determined by both adding increasing quantities of nitromethane to sera and remeasuring the apparent creatinine and by retesting some of the original samples using an enzyme-based creatinine method. RESULTS: We found nitromethane, in the concentrations absorbed or ingested by the patients, increased the apparent creatinine 10- to 20-fold. CONCLUSIONS: Nitromethane interferes with the most widely used colorimetric method used to measure creatinine. Management of this mixed poisoning should focus on the appropriate treatment for methanol toxicity. Extreme, but false, elevations of creatinine do not require hemodialysis when no other significant laboratory abnormality exists.

Laboratory guidelines for monitoring of antimicrobial drugs. National Academy of Clinical Biochemistry.

Few antimicrobial drugs meet the requirements for therapeutic drug monitoring. Those that are monitored include the aminoglycosides (gentamicin, tobramycin, and amikacin), chloramphenicol, and in some cases, vancomycin. For these drugs, there is evidence of a relationship between serum concentration, efficacy, and/or the incidence of adverse or toxic events. Monitoring begins with the appropriate timing of collection and continues through the analytical process to the integration of all data used to guide the clinician's next decision.