Point of care testing provides an accurate measurement of creatinine, anion gap, and osmolal gap in ex-vivo whole blood samples with nitromethane

D. Cao, S. Maynard, Alice Mitchell, W. P. Kerns, M. Beuhler

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

Context. Nitromethane interferes with Jaffé measurements of creatinine, potentially mimicking acute kidney injury. Objectives. We determined the proportional contribution of nitromethane in blood samples to creatinine measured by the Jaffé colorimetric and the point-of-care (POC) reactions and determined whether the difference can reliably estimate the concentration of nitromethane. Additionally, we determined whether the presence of nitromethane interferes with anion/osmolal gaps and ascertained the stability of nitromethane in serum after 7 days. Methods. Nitromethane was added to whole blood from four healthy volunteers to achieve concentrations of 0, 0.25, 0.5, 1, and 2 mmol/L. The following tests were performed: creatinine (Jaffé and POC), electrolytes (associated with Jaffé and POC), osmolality and nitromethane concentration (gas chromatography [GC]). Remaining samples were refrigerated and reanalyzed using GC at 7 days. Anion and osmolal gaps were calculated. Proportional recovery and degradation of nitromethane were measured using GC. Data were analyzed for agreement with single-factor ANOVA (p = 0.05). Results. Mean creatinine for POC and Jaff methods were 0.93 vs. 0.76 mg/dL, respectively. Jaff creatinine concentrations increased linearly with increasing nitromethane concentrations (R2 = 1, p = 0.01): measured creatinine (mg/dL) = 7.1* nitromethane (mmol/L) = 0.79. POC creatinine remained unchanged across the range of nitromethane concentrations (p = 0.99). Anion and osmolal gaps also remained unchanged. Nitromethane was reliably identified in all sample concentrations using GC on Day 0. Detection of 0.25 mmol/L nitromethane was not consistently recovered on Day 7. Nitromethane degradation was most pronounced at 2 mmol/L concentrations (81% recovery). Conclusions. Nitromethane alters apparent concentration of creatinine using the Jaffé reaction in a linear fashion but not when using the POC reaction. Measured difference between Jaffé and POC creatinine may identify the presence and estimate concentration of nitromethane. Presence of nitromethane did not alter the anion or osmolal gap; thus it would not potentially interfere with the diagnosis of co-exposure to a toxic alcohol.

Original languageEnglish (US)
Pages (from-to)611-617
Number of pages7
JournalClinical Toxicology
Volume52
Issue number6
DOIs
StatePublished - 2014

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Acid-Base Equilibrium
Creatinine
Blood
Point-of-Care Systems
Testing
Gas chromatography
Gas Chromatography
Anions
nitromethane
Point-of-Care Testing
Recovery
Degradation
Poisons
Analysis of variance (ANOVA)

Keywords

  • Kidney
  • Metabolic
  • Other

ASJC Scopus subject areas

  • Toxicology

Cite this

Point of care testing provides an accurate measurement of creatinine, anion gap, and osmolal gap in ex-vivo whole blood samples with nitromethane. / Cao, D.; Maynard, S.; Mitchell, Alice; Kerns, W. P.; Beuhler, M.

In: Clinical Toxicology, Vol. 52, No. 6, 2014, p. 611-617.

Research output: Contribution to journalArticle

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title = "Point of care testing provides an accurate measurement of creatinine, anion gap, and osmolal gap in ex-vivo whole blood samples with nitromethane",
abstract = "Context. Nitromethane interferes with Jaff{\'e} measurements of creatinine, potentially mimicking acute kidney injury. Objectives. We determined the proportional contribution of nitromethane in blood samples to creatinine measured by the Jaff{\'e} colorimetric and the point-of-care (POC) reactions and determined whether the difference can reliably estimate the concentration of nitromethane. Additionally, we determined whether the presence of nitromethane interferes with anion/osmolal gaps and ascertained the stability of nitromethane in serum after 7 days. Methods. Nitromethane was added to whole blood from four healthy volunteers to achieve concentrations of 0, 0.25, 0.5, 1, and 2 mmol/L. The following tests were performed: creatinine (Jaff{\'e} and POC), electrolytes (associated with Jaff{\'e} and POC), osmolality and nitromethane concentration (gas chromatography [GC]). Remaining samples were refrigerated and reanalyzed using GC at 7 days. Anion and osmolal gaps were calculated. Proportional recovery and degradation of nitromethane were measured using GC. Data were analyzed for agreement with single-factor ANOVA (p = 0.05). Results. Mean creatinine for POC and Jaff methods were 0.93 vs. 0.76 mg/dL, respectively. Jaff creatinine concentrations increased linearly with increasing nitromethane concentrations (R2 = 1, p = 0.01): measured creatinine (mg/dL) = 7.1* nitromethane (mmol/L) = 0.79. POC creatinine remained unchanged across the range of nitromethane concentrations (p = 0.99). Anion and osmolal gaps also remained unchanged. Nitromethane was reliably identified in all sample concentrations using GC on Day 0. Detection of 0.25 mmol/L nitromethane was not consistently recovered on Day 7. Nitromethane degradation was most pronounced at 2 mmol/L concentrations (81{\%} recovery). Conclusions. Nitromethane alters apparent concentration of creatinine using the Jaff{\'e} reaction in a linear fashion but not when using the POC reaction. Measured difference between Jaff{\'e} and POC creatinine may identify the presence and estimate concentration of nitromethane. Presence of nitromethane did not alter the anion or osmolal gap; thus it would not potentially interfere with the diagnosis of co-exposure to a toxic alcohol.",
keywords = "Kidney, Metabolic, Other",
author = "D. Cao and S. Maynard and Alice Mitchell and Kerns, {W. P.} and M. Beuhler",
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T1 - Point of care testing provides an accurate measurement of creatinine, anion gap, and osmolal gap in ex-vivo whole blood samples with nitromethane

AU - Cao, D.

AU - Maynard, S.

AU - Mitchell, Alice

AU - Kerns, W. P.

AU - Beuhler, M.

PY - 2014

Y1 - 2014

N2 - Context. Nitromethane interferes with Jaffé measurements of creatinine, potentially mimicking acute kidney injury. Objectives. We determined the proportional contribution of nitromethane in blood samples to creatinine measured by the Jaffé colorimetric and the point-of-care (POC) reactions and determined whether the difference can reliably estimate the concentration of nitromethane. Additionally, we determined whether the presence of nitromethane interferes with anion/osmolal gaps and ascertained the stability of nitromethane in serum after 7 days. Methods. Nitromethane was added to whole blood from four healthy volunteers to achieve concentrations of 0, 0.25, 0.5, 1, and 2 mmol/L. The following tests were performed: creatinine (Jaffé and POC), electrolytes (associated with Jaffé and POC), osmolality and nitromethane concentration (gas chromatography [GC]). Remaining samples were refrigerated and reanalyzed using GC at 7 days. Anion and osmolal gaps were calculated. Proportional recovery and degradation of nitromethane were measured using GC. Data were analyzed for agreement with single-factor ANOVA (p = 0.05). Results. Mean creatinine for POC and Jaff methods were 0.93 vs. 0.76 mg/dL, respectively. Jaff creatinine concentrations increased linearly with increasing nitromethane concentrations (R2 = 1, p = 0.01): measured creatinine (mg/dL) = 7.1* nitromethane (mmol/L) = 0.79. POC creatinine remained unchanged across the range of nitromethane concentrations (p = 0.99). Anion and osmolal gaps also remained unchanged. Nitromethane was reliably identified in all sample concentrations using GC on Day 0. Detection of 0.25 mmol/L nitromethane was not consistently recovered on Day 7. Nitromethane degradation was most pronounced at 2 mmol/L concentrations (81% recovery). Conclusions. Nitromethane alters apparent concentration of creatinine using the Jaffé reaction in a linear fashion but not when using the POC reaction. Measured difference between Jaffé and POC creatinine may identify the presence and estimate concentration of nitromethane. Presence of nitromethane did not alter the anion or osmolal gap; thus it would not potentially interfere with the diagnosis of co-exposure to a toxic alcohol.

AB - Context. Nitromethane interferes with Jaffé measurements of creatinine, potentially mimicking acute kidney injury. Objectives. We determined the proportional contribution of nitromethane in blood samples to creatinine measured by the Jaffé colorimetric and the point-of-care (POC) reactions and determined whether the difference can reliably estimate the concentration of nitromethane. Additionally, we determined whether the presence of nitromethane interferes with anion/osmolal gaps and ascertained the stability of nitromethane in serum after 7 days. Methods. Nitromethane was added to whole blood from four healthy volunteers to achieve concentrations of 0, 0.25, 0.5, 1, and 2 mmol/L. The following tests were performed: creatinine (Jaffé and POC), electrolytes (associated with Jaffé and POC), osmolality and nitromethane concentration (gas chromatography [GC]). Remaining samples were refrigerated and reanalyzed using GC at 7 days. Anion and osmolal gaps were calculated. Proportional recovery and degradation of nitromethane were measured using GC. Data were analyzed for agreement with single-factor ANOVA (p = 0.05). Results. Mean creatinine for POC and Jaff methods were 0.93 vs. 0.76 mg/dL, respectively. Jaff creatinine concentrations increased linearly with increasing nitromethane concentrations (R2 = 1, p = 0.01): measured creatinine (mg/dL) = 7.1* nitromethane (mmol/L) = 0.79. POC creatinine remained unchanged across the range of nitromethane concentrations (p = 0.99). Anion and osmolal gaps also remained unchanged. Nitromethane was reliably identified in all sample concentrations using GC on Day 0. Detection of 0.25 mmol/L nitromethane was not consistently recovered on Day 7. Nitromethane degradation was most pronounced at 2 mmol/L concentrations (81% recovery). Conclusions. Nitromethane alters apparent concentration of creatinine using the Jaffé reaction in a linear fashion but not when using the POC reaction. Measured difference between Jaffé and POC creatinine may identify the presence and estimate concentration of nitromethane. Presence of nitromethane did not alter the anion or osmolal gap; thus it would not potentially interfere with the diagnosis of co-exposure to a toxic alcohol.

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KW - Metabolic

KW - Other

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