Effect of lipoprotein (a) on the analytical determination of low-density lipoprotein cholesterol (LDLc) and its influence on pharmacological treatment with atorvastatin.

Lipoprotein(a) (Lp(a)) and Low-density lipoprotein cholesterol (LDLc) is an important risk factor for atherosclerotic cardiovascular disease. The objective of this study was to determine the impact of Lp(a) concentration both on the indirect analytical measurement of LDLc and on the efficacy of dyslipidaemia treatment using the atorvastatin statin. Two retrospective studies were conducted, one with 340 patients and another with 107 patients treated with atorvastatin. Lp(a) concentrations were measured by turbidimetry with an assay independent of the size of the apo(a) isoform. LDLc was calculated using the Friedewald equation and the corrected LDLc was calculated using the Dahlén equation. A strong positive correlation was observed between the serum Lp(a) concentration and the LDLc-overestimation percentage (r = 0.960, p < .001). It was also observed that as the Lp(a) concentration rose there was no significant variation in the percentage decrease in corrected LDLc during atorvastatin treatment (r = 0.186, p > .05). The concentration of LDLc obtained by using the Friedewald equation included Lp(a) cholesterol. The lowering of LDLc in patients treated with atorvastatin depended solely on accessible LDL cholesterol and not on Lp(a) cholesterol.

Assessment of ADVIA Centaur analyzer for the measurement of 25-OH vitamin D.

BACKGROUND: The aim of the present study was to evaluate some analytical performances of the ADVIA Centaur analyzer for the quantitative measurement of 25-OH Vitamin D [25(OH)D] in serum. METHODS: Serum concentrations of 25(OH)D were determined by a new automated chemiluminescence immunoassay method introduced by Siemens and adapted to an ADVIA Centaur analyzer, and compared with HPLC and a commercial chemiluminescence immunoassay (Liaison DiaSorin). RESULTS: The assay displayed a low intra-day (CV < 7.0%) and a low inter-day imprecision (CV < 9.0%). The ADVIA Centaur demonstrated a stronger Spearman's correlation (r = 0.921), better agreement (bias = -0.3 ng/mL), and better concordance correlation coefficient of Lin (P(c) = 0.88) and better kappa index (k = 0.92) with HPLC, than the Liaison DiaSorin assay (r = 0.907, bias = 5.9 ng/mL, p(c) = 0.84, k = 0.60) with HPLC. On the other hand, a significant inverse relationship was observed between parathyroid hormone (PTH) and 25(OH)D concentrations. CONCLUSIONS: The ADVIA Centaur method is reliable for routine 25(OH)D determination in clinical laboratories