Artifactually elevated serum bicarbonate results caused by elevated serum lactate dehydrogenase concentrations

Abstract

Background: An accurate estimation of serum bicarbonate concentration (HCO À 3 ) is essential to the diagnosis and treatment of acid-base disorders and electrolyte disturbances. We noted significant discrepancies between HCO À 3 concentration measured by the Olympus AU2700 analyser and total serum carbon dioxide (TCO 2 ) concentration derived from a Radiometer blood gas analyser on several patient samples. This was reported to the manufacturer which led to a recall of certain reagent lot numbers. We hypothesised the mechanism for this interference to be elevated levels of lactate dehyrogenase (LD). Methods: We investigated the effect of increasing LD concentration on HCO À 3 with the reagent lot that was recalled and compared this with a subsequent reagent lot that was known to be unaffected on an Olympus AU2700. Results: The experimental data confirmed a positive interference in the Olympus AU2700 HCO À 3 assay using older reagent lot numbers. The false positive HCO À 3 interference was significant (>10% change) when the LD concentration exceeded 845 U/L. Conclusions: Very high levels of LD concentrations were the cause of interference in the Olympus AU2700 HCO À 3 enzymatic assay. Laboratorians should be aware that very high levels of LD may be a potential interference in some enzymatic HCO À 3 assays.

Spurious hyperbicarbonatemia and a negative anion gap in a cat and a dog with severe rhabdomyolysis

“…In both cases, the most questionable findings on the biochemistry panel were the markedly increased serum bicarbonate concentration and the negative AG, particularly as rhabdomyolysis typically results in development of metabolic acidosis 1 . An interference involving the measurement of bicarbonate has previously been reported in several species including horses, cattle, humans, and a parrot associated with severe muscle damage, however this is the first published report of this interference in a dog and a cat 2–6 . Of note, in each of these previous reports, similar enzymatic methodology was used for serum bicarbonate measurement.…”

“…The authors hypothesized that the initial bicarbonate reagent lot either lacked oxamate or contained an insufficient amount of this enzyme to inhibit the side reaction involving LDH as they could not replicate the same results when utilizing a different bicarbonate reagent lot. However, the investigators were not able to confirm that oxamate was routinely added to the bicarbonate reagent by the manufacturer 5 . The product sheet for the Beckman Coulter bicarbonate reagent does not include oxamate as an ingredient and repeat analysis of bicarbonate using a different lot number was not attempted, therefore it is unclear what role oxamate may have played in this interference 7…”

“…However, the investigators were not able to confirm that oxamate was routinely added to the bicarbonate reagent by the manufacturer. 5 The product sheet for the Beckman Coulter bicarbonate reagent does not include oxamate as an ingredient and repeat analysis of bicarbonate using a different lot number was not attempted, therefore it is unclear what role oxamate may have played in this interference. 7 It must also be recognized that the mild hemolysis noted in the sera used for biochemical analysis in both cases may have impacted the measurement of CK, AST, and LDH activities.…”

Demonstrating the Analytical Potential of a Wearable Microneedle-Based Device for Intradermal CO2 Detection

“…Notably, HCO 3 – concentrations were obtained by calculations with both techniques (MNs and i-Stat). For the i-Stat, it has been reported that the provided levels may differ from reality, which would explain the differences found with the MNs.…”

A Unique Case of Metformin-Associated Lactic Acidosis

“…In the process there is a decrease in levels of nicotinamide adenine dinucleotide [NADH], which is measured spectrophotometrically by absorbance at 405 nm. The decrease in NADH concentration is then used to calculate the bicarbonate concentration, as there is a direct proportional relationship between the two variables [22]. Based on the Henderson-Hasselbalch equation, a serum bicarbonate concentration of 0 mmol/L is theoretically not possible.…”