Page 207 - HIVMED_v21_i1.indb

Page 13 of 15 Original Research

identifying kidney disease, monitoring of renal function, samples reaching the laboratory after the stability index
drug dosing and selection of ARV drug regimens. Measured time from collection (< 24 h), or if these laboratories decide
GFR was not required for this study as ascertaining the GFR to analyse these serum creatinine samples an appropriate
was not pertinent, but rather the study sought to quantify interpretative comment should be appended to the result as
the clinical significance of the impact of the instability on done for other biochemical analytes such as potassium,
the calculated GFR. The CG equation was the least sensitive glucose, and phosphate. The enzymatic creatinine method
to the effect of the increased creatinine concentrations on is highly recommended in clinical laboratories that
eGFR in our study. This is consistent with a previous finding analyse samples more than 24 h after collection due to
that demonstrated that the CG equation overestimated the transport delays and excessive workload. A major deterrent
eGFR in a large cohort of Europeans, resulting in the concerning the utility of the enzymatic method is its high
43
misclassification of 29.2% of individuals. In contrast, the cost. However, the health costs associated with the
CKD-EPI equation was sensitive to the serum creatinine misclassification of patients using the Jaffe method may
changes of the kinetic Jaffe method, and the impact on the outweigh the analytical costs of the enzymatic method.
eGFR was noted at 24 h. This result is consistent with a Increased demand for the enzymatic method will result in
previous study by Seape and colleagues who found that the competition between suppliers and ultimately reduce the
CKD-EPI equation performed better than other creatinine- cost. This study demonstrated that although creatinine
based eGFR equations when assessing renal function in 100 assays have been standardised the extra analytical
treatment-naïve HIV-positive individuals. 44 considerations which are not standardised may result in
clinically significant creatinine results, thus the use of
Strengths and limitations POCT, which performed well in this study, in remote
clinics may avert the need to perform the laboratory-based
This study was able to show the impact of delayed kinetic Jaffe.
processing of samples on creatinine concentrations on three
platforms with a larger sample size than previous studies. Measurement of creatinine with a POCT provides an
In addition, blood samples were taken from participants at accurate, timely result, and has eliminated the pre-analytical
a single time point and the pre-analytical conditions were problems noted with the kinetic Jaffe method; therefore,
standardised. A limitation of this study is that serum indices adopting of POCT creatinine should be envisaged. The
(such as bilirubin which can falsely elevate creatinine i-STAT POCT creatinine, however, had a negative bias
results) were not considered when evaluating the creatinine which resulted in the misdiagnosis of a renal dysfunction
result. Furthermore, we did not exclude all confounders to for one participant with stage 3a renal failure while the
creatinine measurements such as drugs and pre-existing eGFR of the other 21 participants was not affected. Its
renal dysfunction which may have adversely affected the utilisation in HIV/AIDS programmes could, therefore, be
creatinine results at all time intervals. In addition, we did
not use the reference creatinine method (IDMS) for adopted once the eGFR equations have been validated for
the sample type, confounders of POCT mentioned
comparison purposes; we used an enzymatic method previously and infrastructural issues such as integration
traceable to IDMS. A further limitation is that we did not with the laboratory information systems have been
have a wide range of creatinine concentrations to see how addressed. POCT and enzymatic assays will reduce
a delay in centrifugation would affect the higher unnecessary clinic visits due to renal misdiagnoses (false
concentrations. Furthermore, this study did not explore all positives) and importantly reduce the pill burden, thereby
the risks associated with POCT devices such as lot-to-lot
variation (one lot number was used), operator ultimately reducing health costs to both the government
variability, quality control, analytical traceability, impact of and the patient.
temperature, humidity, different sample types, and the Acknowledgements
different analytical performance of different POCT devices
which have previously been shown to have a significant NHLS medical technologist team from Chris Hani
impact on the eGFR. 45 Baragwanath Hospital, the Alexandra Health Clinic chronic
care team, Mr Philani Buthelezi
Conclusion
This study demonstrated that the Roche kinetic Jaffe method Competing interests
creatinine assay gave falsely elevated serum creatinine The authors have declared that no competing interest exists.
levels if samples were not separated and analysed within 24
h of collection. The increase in the serum creatinine Authors’ contributions
concentration over time was clinically significant resulting
in misclassification of renal status which would, in turn, C.E.C. recruited patients, collected data, obtained ethics
lead to incorrect clinical decisions regarding ARV regimen approval and wrote the first draft. C.P. reviewed and edited
choice. Based on the outputs of this study, and previously the manuscript. D.T. conceptualised the study, reviewed the
published literature, 26,44 laboratories currently analysing statistical analysis, reviewed and edited the manuscript and
creatinine on any Jaffe method should reject (not analyse) approved the final version of the manuscript.

http://www.sajhivmed.org.za 199 Open Access