Reference Interval of Plasma Potassium: A Port Harcourt Based Study

BACKGROUND: Plasma potassium concentration is influenced by dietary intake of potassium when all other parameters that control potassium homeostasis are normal. Studies have shown significantly different potassium means across regions and since blood potassium concentration is important in the management of kidney, heart and organ transplant patients among others, it is, therefore, important to determine our own population-based reference interval. AIM: This study was to determine the reference interval of plasma potassium in this geographical region. METHODS: This was a retrospective study where results from the laboratory day sheets of patients who met the inclusion criteria were selected over a period of six months. This results were determined using ISE LWE60E by Landwind. This results were ranked and outliers removed and the mean calculated. The 2.5th percentile was calculated and used as the lower limit while the 97.5th percentile was determined and used as the upper limit. RESULTS: The mean age and result of the study population were 45.2 years and 4.3mmol/l, respectively. The reference interval was 2.4- 4.7mmol/l. CONCLUSION: The reference interval so determined in this study is about the same with those determined from other locations in Nigeria but significantly different from that of Caucasians. Most of the lower limits of the reference interval determined in Nigeria were below 3.0mmol/l. This is significant as it calls for a re-definition of grading hypokalaemia.