Clin Chem Lab Med 2015; 53(12): e325–e327
Letter to the Editor Giuseppe Lippi*, Gian Luca Salvagno and Gian Cesare Guidi
Adjustment of serum potassium for age and platelet count. A simple step forward towards personalized medicine DOI 10.1515/cclm-2015-0324 Received April 6, 2015; accepted April 30, 2015; previously published online June 2, 2015
Keywords: personalized medicine; platelet; potassium; reference range.
To the Editor, Potassium, a metallic inorganic ion, is the most abundant cation in human body. The vast majority of this ion is contained in the intracellular compartment, with residual amount present in the extracellular space [1]. The reference range of serum potassium is typically comprised between 3.5 and 5.5 mmol/L, and no substantial variation has been described according to age and gender [1]. A pathological increase of potassium in serum, conventionally known as hyperkalemia (i.e., > 5.5 mmol/L), is associated with significant morbidity and mortality, so that its timely identification and correction are of outmost clinical significance [2]. Although hyperkalemia is frequently observed in patients with renal failure, adrenal insufficiency and rhabdomyolysis, spurious elevation of serum level of potassium can be found in association with an elevated platelet count due to the release from platelet granules during coagulation, but also in the presence of erythrocytosis due to dilution of this ion in smaller volumes of serum [3]. The presence of these conditions may hence
*Corresponding author: Prof. Giuseppe Lippi, Laboratory of Clinical Chemistry and Hematology, Academic Hospital of Parma, Via Gramsci 14, 43126 Parma, Italy, Phone: +39 0521 703050/ +39 0521703791, E-mail: [email protected]; [email protected]; and Laboratory of Clinical Chemistry and Hematology, Academic Hospital of Parma, Parma, Italy. http://orcid.org/0000-0001-9523-9054 Gian Luca Salvagno and Gian Cesare Guidi: Department of Medicine and Department of Life and Reproduction Sciences, University Hospital of Verona, Verona, Italy
impair the clinical reasoning, since pseudohyperkalemia may trigger inappropriate diagnostic and therapeutic decisions. In order to identify important determinants of serum potassium concentration in healthy subjects, we carried out a retrospective analysis of serum potassium, serum creatinine and hematological data in a cohort of regular blood donors aged > 20 years who were not taking any medication, and who were admitted to the transfusion service for routine check-up over a 1-year period (from January to December 2014). Correlation between variables was assessed by univariate (Spearmen’s regression) and multivariate analysis, in which potassium was entered as the dependent variable. The reference range was calculated according to the reference Clinical and Laboratory Standards Institute (CLSI) document C28-A2 [4], using Analyse-it (Analyse-it Software Ltd, Leeds, UK). The study was performed in accordance with the Declaration of Helsinki and under the terms of all relevant local legislation. Cumulative laboratory results of laboratory tests could be identified for 322 blood donors throughout the study period (mean age, 51±16 years; 81 females and 241 males). The mean value and the reference range of serum potassium in the entire study population were 3.93 mmol/L and 3.28–4.57 mmol/L, respectively. The low upper limit of the reference interval is due to the fact that the study population included healthy blood donors, whose values may be more “normal” than those of the general population. In univariate analysis, serum potassium values were found to be significantly and positively associated with age and platelet count, whereas no significant association was observed with gender, serum creatinine, white blood cell and red blood cell counts (Table 1). In multivariate a nalysis, age (β coefficient, 0.005; p
Letter to the Editor Giuseppe Lippi*, Gian Luca Salvagno and Gian Cesare Guidi
Adjustment of serum potassium for age and platelet count. A simple step forward towards personalized medicine DOI 10.1515/cclm-2015-0324 Received April 6, 2015; accepted April 30, 2015; previously published online June 2, 2015
Keywords: personalized medicine; platelet; potassium; reference range.
To the Editor, Potassium, a metallic inorganic ion, is the most abundant cation in human body. The vast majority of this ion is contained in the intracellular compartment, with residual amount present in the extracellular space [1]. The reference range of serum potassium is typically comprised between 3.5 and 5.5 mmol/L, and no substantial variation has been described according to age and gender [1]. A pathological increase of potassium in serum, conventionally known as hyperkalemia (i.e., > 5.5 mmol/L), is associated with significant morbidity and mortality, so that its timely identification and correction are of outmost clinical significance [2]. Although hyperkalemia is frequently observed in patients with renal failure, adrenal insufficiency and rhabdomyolysis, spurious elevation of serum level of potassium can be found in association with an elevated platelet count due to the release from platelet granules during coagulation, but also in the presence of erythrocytosis due to dilution of this ion in smaller volumes of serum [3]. The presence of these conditions may hence
*Corresponding author: Prof. Giuseppe Lippi, Laboratory of Clinical Chemistry and Hematology, Academic Hospital of Parma, Via Gramsci 14, 43126 Parma, Italy, Phone: +39 0521 703050/ +39 0521703791, E-mail: [email protected]; [email protected]; and Laboratory of Clinical Chemistry and Hematology, Academic Hospital of Parma, Parma, Italy. http://orcid.org/0000-0001-9523-9054 Gian Luca Salvagno and Gian Cesare Guidi: Department of Medicine and Department of Life and Reproduction Sciences, University Hospital of Verona, Verona, Italy
impair the clinical reasoning, since pseudohyperkalemia may trigger inappropriate diagnostic and therapeutic decisions. In order to identify important determinants of serum potassium concentration in healthy subjects, we carried out a retrospective analysis of serum potassium, serum creatinine and hematological data in a cohort of regular blood donors aged > 20 years who were not taking any medication, and who were admitted to the transfusion service for routine check-up over a 1-year period (from January to December 2014). Correlation between variables was assessed by univariate (Spearmen’s regression) and multivariate analysis, in which potassium was entered as the dependent variable. The reference range was calculated according to the reference Clinical and Laboratory Standards Institute (CLSI) document C28-A2 [4], using Analyse-it (Analyse-it Software Ltd, Leeds, UK). The study was performed in accordance with the Declaration of Helsinki and under the terms of all relevant local legislation. Cumulative laboratory results of laboratory tests could be identified for 322 blood donors throughout the study period (mean age, 51±16 years; 81 females and 241 males). The mean value and the reference range of serum potassium in the entire study population were 3.93 mmol/L and 3.28–4.57 mmol/L, respectively. The low upper limit of the reference interval is due to the fact that the study population included healthy blood donors, whose values may be more “normal” than those of the general population. In univariate analysis, serum potassium values were found to be significantly and positively associated with age and platelet count, whereas no significant association was observed with gender, serum creatinine, white blood cell and red blood cell counts (Table 1). In multivariate a nalysis, age (β coefficient, 0.005; p
