Correction of patient results for Beckman Coulter LX-20 assays affected by interference due to hemoglobin, bilirubin or lipids: a practical approach

Abstract

The influence of interference by hemolysis, icterus and lipemia on the results of routine chemistries may lead to wrong interpretations. On Synchron LX-20 instruments (Beckman Coulter) serum or plasma indices can be used as reliable semi-quantitative measures of the magnitude of such interference. In an article recently published in this journal, we presented the results of a multicenter study carried out in Dutch hospitals in which we determined cutoff indices for analytes above which analytically significant interference exists. Clinically significant interference cutoff indices were also derived for these analytes. In this article, we describe the handling of patient samples with clinically significant interference by hemolysis, icterus or lipemia. We investigated several possible approaches for correction of the result: dilution of the interference; mathematical correction in the case of hemolysis; treatment with ferrocyanide to destroy bilirubin; and removal of lipids in lipemic patient samples. We concluded, that mathematical correction of potassium or lactate dehydrogenase results in hemolytic samples can only be carried out if intravascular hemolysis is ruled out. Hemoglobin quantification in serial patient samples, combined with measurement of haptoglobin, represents a useful tool to rule out in vivo hemolysis. We derived an algorithm for this situation. We do not simply recommend mathematical correction, unless it is clinically acceptable. We present formulas for potassium and lactate dehydrogenase: corrected potassium=measured potassium-(hemolytic index increment x 0.14); corrected lactate dehydrogenase=measured lactate dehydrogenase-(hemolytic index increment x 75). The dilution studies indicated that dilution is only applicable for bilirubin, C-reactive protein and iron. The results of treatment with ferrocyanide were poor, and we do not recommend this method. Removal of lipids using high-speed centrifugation or LipoClear (StatSpin Inc.), a non-toxic and non-ionic polymer, is a very effective approach, although C-reactive protein, creatine kinase-MB (CK-MB) and cholesterol cannot be removed using LipoClear. For all interferants (hemoglobin, bilirubin, lipids), relatively simple algorithms are derived that can easily be implemented in the clinical laboratory.

Potassium but Not Lactate Dehydrogenase Elevation Due To In Vitro Hemolysis Is Higher in Capillary Than in Venous Blood Samples

“…Linear regression analysis revealed a 0.38 mEq/L (95% confidence interval, 0.36-0.40; conversion to SI units: 1 mEq/L 5 1 mmol/L) potassium increase per increment in H-index for capillary samples, which is more than twice as high as the 0.17 mEq/L (95% confidence interval, 0.16-0.17) increase found for venous samples. The latter result corresponds well with the potassium increase of 0.14 mEq/L per H-index increment described by Vermeer et al, 3 thereby supporting the validity of the current method. The identical offset of 4.1 mEq/L indicates that there are no intrinsic differences in potassium levels between venous and capillary samples, which is in correspondence with previously published results.…”

“…3,4 Based on the linear relation between potassium and H-index, correction factors might be derived to adjust the measured potassium level to the extent of hemolysis. [3][4][5][6][7][8][9][10][11][12][13][14][15] Although this would produce representative potassium values in most cases, it fails in cases of intravascular hemolysis. Given that intravascular hemolysis is rare (less than 2% of the hemolytic samples, as shown for an Italian academic hospital 6 ), potassium correction based on high H-indices is not justified in these cases.…”

Multicenter evaluation of the hemolysis index in automated clinical chemistry systems

“…globin-based oxygen carriers (14), which would ultimately help diminish uncertainty in the preanalytical phase, enhance the quality in laboratory diagnostics, and reduce the chance of errors that can jeopardize the patient safety (7). Although the approach has been previously questioned (7), it is necessary to mention that the availability of quantitative results of hemoglobin in the samples might allow the use of formulas for correcting biases due to interference from hemolysis (15). Although most preanalytical workstations and clinical chemistry platforms are now equipped with automatic systems for detecting, and some for quantitating interferents, no studies have previously assessed imprecision and reproducibility of these measures among facilities and, especially, among different instruments and manufacturers.…”

Cyclodextrin Removal of Lipemic Interference: An Attractive Alternative to Ultracentrifugation for Satellite Laboratories

“…Previous work has compared preanalyte and postanalyte measurements on the Beckman Synchron LX-20, after artificial spiking of nonlipemic samples with the synthetic lipid Intralipid (Uppsala, Sweden). 4 In this study, no discordance between recovery with ultracentrifugation and LipoClear was observed with sodium or total protein, highlighting potential limitations for Intralipid as a universal substitute for assessing endogenous lipemic interferences. Additionally, 78% of LipoClear-treated samples showed lower lipemia indices after treatment than did their paired ultracentrifuged specimens, suggesting a more-complete removal of interfering lipids.…”