Non-linearity in lipase assays: A multicentric comparison on different analysers

OBJECTIVES

Non-linearity in lipase assays and the ensuing gaps in results distribution have been described on Roche analysers, but have yet to be studied on other analysers.

DESIGN AND METHODS

Eighteen lithium-heparinized plasma pools of lipase activities decreasing from 1700 to <4 U/L were prepared for multicentric evaluation on several analysers. Non-linearity was modelled as the difference between the polynomial regression of lipase activities depending on relative dilutions over the primary measuring range, and the linear regression of the same variables above the manufacturer's limit of linearity (MLL). Gaps in lipase distribution resulting from non-linearity were graphically evidenced through histograms. Upper limits of gaps were calculated, which are lipase activities where non-linearity biases no longer impact the diluted lipase results.

RESULTS

MLLs and lipase (U/L) calculated at MLL (%biases versus MLL) were respectively: 1200 and 1124 (-6.3%) on the Architect C16000 (Abbott); 300 and 248 (-17.3%) on the Cobas c503 (Roche); 1500 and 1458 (-2.8%) on the Dimension Vista (Siemens); and 700 and 659 (-5.9%) on the Atellica CH930 (Siemens). Using Sentinel Lipase reagents on Abbott analysers, these measurements were respectively: 300 and 294 (-2.0%) on the Architect C16000, and 300 and 298 (-0.7%) on the Alinity. Setting Randox Lipase reagents on the Alinity, MLL and lipase at MLL were 953 and 776 (-18.6%), respectively.

CONCLUSIONS

Considering the desirable (±14.2 %) and optimal (±7.1 %) allowable total error for lipase (EFLM/EuBIVAS), biases at manufacturer's limit of linearity were acceptable, except for Roche Cobas c503 method and Randox method on Abbott Alinity.

Autophagosome maturation is impaired in Fabry disease

Fabry disease is a lysosomal storage disorder (LSD) caused by a deficiency in α-galactosidase A. The disease is characterized by severe major organ involvement, but the pathologic mechanisms responsible have not been elucidated. Disruptions of autophagic processes have been reported for other LSDs, but have not yet been investigated in Fabry disease. Renal biopsies were obtained from 5 adult male Fabry disease patients before and after 3 years of enzyme replacement therapy (ERT) with agalsidase alfa. Vacuole accumulation was seen in renal biopsies from all patients compared with control biopsies. Decreases in the number of vacuoles were seen after 3 years of ERT primarily in renal endothelial cells and mesangial cells. Measurement of the levels of LC3, a specific autophagy marker, in cultured cells from Fabry patients revealed increased basal levels compared to cells from non-Fabry subjects and a larger increase in response to starvation than seen in non-Fabry cells. Starvation in the presence of protease inhibitors did not result in a significant increase in LC3 in Fabry cells, whereas a further increase in LC3 was observed in non-Fabry cells, an observation that is consistent with impaired autophagic flux in Fabry disease. Overexpression of LC3 mRNA in Fabry fibroblasts compared to control cells is consistent with an upregulation of autophagy. Furthermore, LC3 and p62/SQSTM1 (that binds to LC3) staining in renal tissues and in cultured fibroblasts from Fabry patients supports impairment of autophagic flux. These findings suggest that Fabry disease is linked to a deregulation of autophagy.

Diesel exhaust particles are taken up by human airway epithelial cells in vitro and alter cytokine production

The involvement of diesel exhaust particles (DEPs) in respiratory diseases was evaluated by studying their effects on two in vitro models of human airway epithelial cells. The cytotoxicity of DEPs, their phagocytosis, and the resulting immune response were investigated in a human bronchial epithelial cell line (16HBE14o-) as well as in human nasal epithelial cells in primary culture. DEP exposure induced a time- and dose-dependent membrane damage. Transmission electron microscopy showed that DEPs underwent endocytosis by epithelial cells and translocated through the epithelial cell sheet. Flow cytometric measurements allowed establishment of the time and dose dependency of this phagocytosis and its nonspecificity with different particles (DEPs, carbon black, and latex particles). DEPs also induced a time-dependent increase in interleukin-8, granulocyte-macrophage colony-stimulating factor, and interleukin-1beta release. This inflammatory response occurred later than phagocytosis, and its extent seems to depend on the content of adsorbed organic compounds because carbon black had no effect on cytokine release. Furthermore, exhaust gas posttreatments, which diminished the adsorbed organic compounds, reduced the DEP-induced increase in granulocyte-macrophage colony-stimulating factor release. These results suggest that DEPs could 1) be phagocytosed by airway epithelial cells and 2) induce a specific inflammatory response.