Abstract
Objective Electrolyte, hemoglobin, and bilirubin values are routinely reported with point-of-care
(POC) testing for blood gases. Results are rapidly available and require a small blood
volume. Yet, these results are underutilized due to noted discrepancies between central
laboratory (CL) and POC testing. The study aimed to determine the correlation between
POC and CL measurement of electrolytes, hemoglobin, and bilirubin in neonates.
Study Design Electrolyte, hemoglobin, and bilirubin results obtained from capillary blood over
a 4-month period were analyzed. Each CL value was matched with a POC value from the
same sample or another sample less than 1-hour apart. Agreement was determined by
measuring the mean difference (MD) between paired samples with 95% limits of agreement
(LOA) and Lin's concordance correlation (LCC).
Results There were 355-paired sodium/potassium, 139 paired hemoglobin, and 197 paired bilirubin
values analyzed. POC sodium values were lower (133.5 ± 5.8 mmol/L) than CL (140.2 ± 5.8 mmol/L),
p <0.00001 with poor agreement (LCC = 0.49; MD = 6.7; 95% LOA: −13.6 to 0.14). POC
potassium values were lower (4.6 ± 0.98 mmol/L) than CL (4.98 ± 1.24mEq/L), p < 0.0001, but with better concordance and agreement. (LCC = 0.6; MD = 0.4; 95% LOA:
−2.3 to 1.4). There were no differences in hemoglobin between POC (14.3 ± 3.2 g/dL)
and CL (14.4 ± 3.1 g/dL), p = 0.2 with good LCC (0.93) and in bilirubin values between POC (6.0 ± 3.2 mg/dL)
and CL (5.8 ± 3.0 mg/dL), MD = 0.18, and p = 0.07.
Conclusion POC Sodium values are lower than CL. POC potassium levels are also lower, but the
differences may not be clinically important while hemoglobin and bilirubin levels
are similar between POC and CL. As POC potassium, hemoglobin, and bilirubin levels
closely reflect CL values, these results can be relied upon to make clinical judgments
in neonates.
Key Points
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Electrolyte, hemoglobin, and bilirubin are available as POC.
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POC sodium and potassium values are lower than CL results.
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Hemoglobin and bilirubin values are similar between POC and CL.
Keywords
electrolytes - sodium - potassium - hemoglobin - bilirubin - point of care - neonatal
intensive care
