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Indian Journal of Critical Care Medicine
Medknow Publications on behalf of the Indian Society of Critical Care Medicine
ISSN: 0972-5229 EISSN: 1998-359x
Vol. 15, Num. 3, 2011, pp. 196-197

Indian Journal of Critical Care Medicine, Vol. 15, No. 3, July-September, 2011, pp. 196-197

Letter to the Editor

Authors' reply

1 Medical ICU, Christian Medical College & Hospital, Vellore, India
2 Department of Biochemistry, Christian Medical College & Hospital, Vellore, India
3 Department of Clinical Biochemistry, Christian Medical College & Hospital, Vellore, India
Correspondence Address: John Victor Peter, Medical Intensive Care Unit, Christian Medical College & Hospital, Ida Scudder Road, Vellore - 632 004, India, peterjohnvictor@yahoo.com.au

Code Number: cm11054

Sir,

The authors have raised some queries [1] on our submission. [2] We agree with the statement, "two samples that are processed in different times can have different laboratory data". In our paper, we have stated that paired samples were collected at the same time from each patient. Thus, time difference in assay was small and unlikely to contribute to the differences observed.

As pointed out, data on quality control and reference ranges of the two systems are important. The % co-efficient of variation for both analyzers has been described in detail in the Section "Materials and Methods". Since the two analyzers use different samples (whole blood vs. serum), it was not possible to use the same quality control materials for both the analyzers, particularly as the manufacturer often compensates the material specifically for the conditions of their analyzer.

As regards the reference range, no specific reference range was used for whole blood samples. However, following this study, a lower range probably needs to be defined for whole blood samples, given that the whole blood potassium was lower by 0.3 mEq/L and sodium was lower by 4.0 mEq/L. As correctly pointed in the letter, our study determined a correction factor between arterial whole blood and serum and not between arterial whole blood samples (that is commonly analyzed at point of care) and venous serum samples (that are usually sent to the central laboratory). Thus, as stated in our paper, each center needs to do its own study to determine the correction factor that needs to be applied for the different types of samples that are sent for testing.

References

1.Wiwanitkit V. Electrolytes assessed by point-of-care testing. Indian J Crit Care Med 2011;15:196  Back to cited text no. 1    
2.Chacko B, Peter JV, Patole S, Fleming JJ, Selvakumar R. Electrolytes assessed by point-of-care testing: Are the values comparable with results obtained from the central laboratory? Indian J Crit Care Med 2011;15:24-9.  Back to cited text no. 2  [PUBMED]  Medknow Journal

Copyright 2011 - Indian Journal of Critical Care Medicine

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