Automated Processing of Serum Indices Used for Interference Detection by the Laboratory Information System

Abstract

In this report, we focus on improvements in patient results with respect to interferences in analytical results obtained from a routine chemistry analyzer (Synchron LX20PRO; Beckman Coulter Inc.). Although many authors have reported on improvements in process performance to reduce analytical errors, assay interference by endogenous or exogenous substances is an underrated problem with potential detrimental effects for the patient (1)(2)(3). Four major endogenous compounds that often interfere with most laboratory results are hemoglobin, bilirubin, lipids, and paraproteins (3)(4)(5). In our laboratory, the vast majority of hemolyzed samples (>95%) are attributable to in vitro processes resulting from incorrect sampling procedures or transport (6). Icteric or lipemic samples are indicative of a physiologically, and possibly clinically, important process. Although differentiating between in vivo and in vitro hemolysis is clinically important, extensively hemolyzed samples may be difficult to evaluate (6)(7). The frequency of interferences in clinical laboratory analyses is very difficult to determine (3). In principle, interferences can be reduced by use of adequately blanked analytical methods (8). Graphical displays of instrument- and analyte-specific interferences have been produced previously (6)(9). The LX20 analyzer has the capability to detect hemolysis, icterus, and lipemia in samples and produces semiquantitative unitless index values for hemoglobin, bilirubin, or Intralipid (so-called serum indices), but these serum index functions are not intended for diagnostic purposes. With increasing amounts of the specific interfering compounds, increasing index values are generated, which are linearly correlated with the amount of interferent. We assessed the effect of interference by hemolysis, icterus, or lipemia on various analytes, using interference data provided by the manufacturer (Beckman Coulter, Inc.), experimental data from three Dutch hospitals, and our own research. We performed interference studies with serum pools to which interferent solutions were added (up …