|Year : 2016 | Volume
| Issue : 2 | Page : 45
Discrepancies in interlaboratory plasma bicarbonate measurement
Elaine Chinyelu Azinge
The Editor-in-Chief, Journal of Clinical Sciences, The Office of the Dean, Faculty of Clinical Sciences, College of Medicine, University of Lagos, PMB 12003, Idi Araba, Lagos, Nigeria
|Date of Web Publication||4-Apr-2016|
Elaine Chinyelu Azinge
The Editor-in-Chief, Journal of Clinical Sciences, The Office of the Dean, Faculty of Clinical Sciences, College of Medicine, University of Lagos, PMB 12003, Idi Araba, Lagos
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Azinge EC. Discrepancies in interlaboratory plasma bicarbonate measurement. J Clin Sci 2016;13:45
The bicarbonate content of plasma is a significant indicator of the buffering capacity of that individual. Bicarbonate is the second, largest fraction of the anions of plasma,  measured as these fractions are bicarbonate, carbon dioxide in solution, and carbimino compounds. , The reference range of bicarbonate is 22-29 mmol/L. , Together with hydrogen concentration, bicarbonate is used in the diagnosis of serious disorders of acid-base balance in clinical medicine. , These are disorders that affect the respiratory and metabolic systems of the body. Important causes of acid-base dysfunction include diarrhea, chronic renal failure, diabetic ketoacidosis, and renal tubular acidosis. 
Quite often in this locality, requests from the same patient are sent to different laboratories for analysis and often enough discrepancies often arise in the measurement of plasma bicarbonate, especially in pediatric patients where the volume of drawn blood is low.  The practice of sending the same sample to different laboratories arose in recent times as a result of poor funding and infrastructural decay found in government laboratories and its attendant consequences. For this reason, it is important to highlight preanalytical causes of discrepancies in bicarbonate measurements. ,, Phlebotomy errors cause 24-30% of serious patient misdiagnosis. Inadequate filling of specimen tubes which usually occurs in pediatric subjects causes a significant decline in bicarbonate measurement known as pseudometabolic acidosis. The cause of this is inadequate anticoagulant/blood ratio. , Also, because the determination of bicarbonate includes dissolved carbon dioxide, this fraction will escape into the air once the stopper of the specimen bottle is removed from the sample tube. The escape of carbon dioxide can cause a decrease of up to 6 mmol/L in the course of 1 h. ,
Separated plasma should not be left at 15-30°C for longer than 8 h.  The sample must be stored at 2-8°C if it is going to be stored for longer than 48 h and should be thawed only once. Analyte deterioration is usually found in repeatedly thawed and frozen samples.  If the logistics in different laboratories are different, the extent of error will be different. These are some of the causes of discrepancies in results from the same patient analyzed in different laboratories. 
Discrepancies can also arise as a result of the choice of methodology.  There are titrimetric, enzymatic, and calculated methods of measuring bicarbonate. , Different laboratories adopt different methods depending on how well funded the laboratory is.
The reference ranges of bicarbonate differ with age:
- 0-7 days is 13-26 mmol/L
- 7 days-15 years is 20-30 mmol/L
- >15 years is 22-29 mmol/L ,
- Critical call results are values <10 mmol/L or >40 mmol/L
- These must be sent urgently to the consulting physician. 
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