POC device reliable for measuring creatinine in kids

A point-of-care (POC) blood gas analyser yields accurate creatinine measurements in paediatric patients and may be used for the diagnosis of postoperative acute kidney injury (AKI) when combined with lab results, according to a recent study.

“Despite the excellent agreement between the two methods and the potential advantage of easy access and frequent information by the POC device, we need careful discussion before using [this tool] frequently for diagnosis of AKI based on KDIGO* criteria for paediatric patients because of the discordant diagnosis of AKI between the two methods, as shown in our study,” researchers said.

From 498 retrospectively assessed paediatric patients who had undergone cardiac surgery (median age, 14 months; 53.4 percent male), the researchers obtained 1,404 paired creatinine measurements. The median time gap between POC device and central lab measurements was 25 minutes. [Health Sci Rep 2019;doi:10.1002/hsr2.143]

Researchers found that the correlation between measurements was good, with a Pearson correlation coefficient of 0.968 (95 percent confidence interval [CI], 0.965–0.972; p<0.001). Taking the average of the repeated measures for each participant, the Pearson correlation coefficient climbed slightly to 0.975 (95 percent CI, 0.971–0.979).

The resulting median bias between the two measurement methods was 0.02 mg/dL, with a 95 percent limit of agreement ranging from –0.137 to 0.178 mg/dL.

“Our study, which is the first one to assess the performance of a POC device exclusively on patients younger than 18 years of age, supports the clinical usefulness of [a POC blood gas analyser for creatinine] for patients with a wide range of ages, when taken together with the results of the other studies,” the researchers said.

On the other hand, the POC device appears to underperform when it comes to AKI diagnosis. In the postoperative period, 71.7 percent (n=357) were diagnosed by the blood gas analyser to have AKI. This represented a 161-patient discrepancy relative to lab measurements, which identified AKI in only 40.0 percent (n=199).

Three patients who were diagnosed with AKI using POC measurements were artefactual when compared with lab results.

Notably, a small-time gap between the two methods of creatinine measurement led to better concordance. In 250 patients where both POC and lab measurements were within 1 hour of each other, the rates of AKI identification were 46.0 percent and 42.8 percent, respectively.  

“Although a discordant diagnosis of postoperative AKI based on KDIGO criteria was found in about one third of the paediatric patients between the two methods when using all the measurements, the paired measurements with a small-time gap showed a good agreement on AKI diagnosis,” said the researchers.

“Additional studies are needed to show the efficacy of frequent creatinine measurements by POC devices for diagnosis of AKI based on KDIGO criteria for paediatric patients,” they added.

*Kidney Disease Improving Global Outcomes