The Difference Between Glucose Level Measured From K2-EDTA Plasma and Serum Samples

XXXIII. WASPaLM World Congress & XXIV. National Clinicial Biochemistry Congress, Antalya, Türkiye, 16 - 20 Ekim 2024, ss.161

Introduction: Glucose is one of the most frequently analyzed parameter in biochemistry laboratories,

owing to its significant role in Diabetes Mellitus diagnosis and fallow up. Studies on the difference of

glucose level in serum and plasma samples revealed different results. Researches pointed out that,

plasma samples are centrifuged immediately then analyzed. In contrast serum samples are waited for

the blood to clot. Thus, less ex-vivo glycolysis occurs in plasma samples compared with serum

samples. This study aimed to compare glucose levels between plasma and serum samples centrifuged

and analyzed at the same time.

Method: Samples of 20 patient, with glucose and complete blood count or Hba1c requests with the

same order number, were taken and brought to our laboratory at the same time, included in this study.

The patients' tubes containing clot activator and K2-EDTA were centrifuged together at the

recommended speed and time. Obtained serum and plasma samples were separated and analyzed

twice. The mean of each sample results were calculated. Passing-Bablok regression and Bland-Altman

plot were used to evaluate the consistency between serum and plasma glucose levels.

Results: The evaluation was carried out on serum (N= 20) and plazma (N= 20) glucose result. The

linear range of glucose in both samples was between 76.7 and 250.9 mg/dL. Median glucose levels in

serum and plazma sample were 90.1 (83 - 96.4) mg/dL and 93.4 (88.1 - 105.5) mg/dL, respectively.

There was a high concordance between the two samples. In the Passing-Bablok analyses, the 95%

confidence intervals of the slope and intercept parameters were (0.990 to 1.054) and (-2.027 to 4.959),

respectively. within the acceptable ranges. The regression equation is y= 2.477 + 1.009 x, with a

correlation coefficient r= 0.968 (P< 0.001). There was no statistically significant deviation from

linearity (P= 0.72). The Bland-Altman diagram shows that the percent bias between the two samples is

%3.8 (95%CI, 2.35 - 5.25) as the glucose levels were higher in plasma than serum sample.

Conclusion: According to the results, a good agreement between the two sample glucose

measurements was seen. It is possible to say that both samples are comparable for glucose

measurement because there is a positive and strong linear relationship between these two samples.

However, laboratory and clinical physicians should be aware of the difference between these two

samples when evaluating patients’ glucose results.

Keywords: Glucose, comparison, plasma, serum, specimen handling.