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Evaluation of a new handheld biosensor for point-of-care
testing of whole blood beta-hydroxybutyrate concentration
RWK Chiu, CS Ho, SF Tong, KF Ng, CW Lam
Department of Chemical Pathology, The Chinese University of Hong
Kong, Prince of Wales Hospital, Shatin, Hong Kong
OBJECTIVES. To evaluate performance characteristics
of the newly available handheld combined glucose and ketone meter
for beta-hydroxybutyrate measurement.
DESIGN. Laboratory method evaluation.
MAIN OUTCOME MEASURES. Accuracy of beta-hydroxybutyrate measurement
and effect of acetoacetate interference at clinically important
beta-hydroxybutyrate levels.
RESULTS. Deming regression analysis of beta-hydroxybutyrate measurements
assessed by the ketone sensor and a laboratory enzymatic method
revealed a coefficient of determination of 0.989 (P<0.001). Passing-Bablok
regression analysis showed a linear relationship between the two
methods, ie Y= –0.32+1.13X. The 95% confidence interval of
the slope and y-intercept were: slope=1.13 (95% confidence interval,
1.04 to 1.22); intercept= –0.32 (95% confidence interval, -0.59
to -0.06). The Bland-Altman plot showed a small proportional bias
between the two methods. The mean bias ±2 standard deviations
was between -0.53 and 0.67 mmol/L. Beta-hydroxybutyrate measurements
made by the sensor were linear up to 6 mmol/L. Replicate analysis
of two samples spiked with 3.6 mmol/L and 0.8 mmol/L of beta-hydroxybutyrate
resulted in coefficients of variation of 3.3% and 13%, respectively.
The presence of acetoacetate caused a negative interference in beta-hydroxybutyrate
measurement. Beta-hydroxybutyrate recovery was 97.0% and 90.7% when
the ketone body ratios were 6:1 and 3:1, respectively.
CONCLUSION. The analytical performance of the sensor, when operated
according to manufacturer’s instructions, could meet the needs
of point-of-care beta-hydroxybutyrate measurement. Additional clinical
studies are needed to assess the benefits of introducing such an
assay in a clinical setting.
Hong Kong Med J 2002;8:172-6
Key words: 3-Hydroxybutyric acid; Ketones; Point-of-care
systems
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