Cancer Diagnosis Program | Biorepositories and Biospecimen Research Branch

Search BRD Papers

Postural change during venous blood collection is a major source of bias in clinical chemistry testing.

Author(s): Lippi G, Salvagno GL, Lima-Oliveira G, Brocco G, Danese E, Guidi GC

Publication: Clin Chim Acta, 2015, Vol. 440, Page 164-8

PubMed ID: 25437911 PubMed Review Paper? No

Purpose of Paper

Conclusion of Paper

Studies

1. Study Purpose

   This study investigated if patient posture during blood draw affects levels of clinical chemistry analytes in serum and EDTA blood and also investigated if patient age, body mass index, height, weight, or gender influenced the effect of posture on plasma volume. Three fasting venous blood specimens were obtained from each of 19 healthy volunteers into serum vacuum tubes with clot activator and gel separator and K2EDTA vacuum tubes. The first specimen was drawn after the volunteer was supine for 25 min, the second after 20 minutes sitting, and the third after 20 min upright. Serum specimens were centrifuged at 1300 x g for 15 min and levels of albumin, ALP, alanine aminotransferase (ALT), alpha-amylase, AST, bilirubin total and conjugated, calcium, cholesterol total and HDL, chloride, creatine kinase (CK), creatinine, CRP, GGT, glucose, iron, LDH, lipase, magnesium, phosphate, potassium, total protein, sodium, triglycerides, urea, and uric acid were measured on a Cobas c501. Hematocrit and hemoglobin were measured in K2EDTA blood using an Advia 2120. The authors did not address the potential effects of sequential blood sampling on the results. The quality specifications for bias were based on biological variation. 

   Summary of Findings:

   When the patient was sitting for 20 min before blood draw, the plasma volume was 3.4% lower than when the patient had been supine for 25 min and 9.7% higher than when the patients had been standing for 20 min. The effect of patient posture on plasma volume was not correlated with patient age, body mass index, gender, weight, or height. Compared to sitting patients, supine patients had statistically significantly lower levels of hemoglobin (-2.3%, P<0.001), hematocrit (-1.7%, P=0.009), albumin (-2.0%, P=0.001), ALP (-3.6%, P<0.001), ALT (-2.0%, P=0.035), amylase (-2.6%,  P<0.001), AST (-4.5%, P=0.001), total  cholesterol (-2.5%, P<0.001), HDL cholesterol (-3.1%, P<0.001), CK -2.5%, P<0.001), GGT (-4.2%, P=0.001), iron (-1.4%, P=0.008), LDH (-2.3%, P=0.045), magnesium (-1.4%, P=0.001), total protein (-2.9%, P=0.003), and triglycerides (-5.1%, P=0.021) and significantly higher levels of urea  (1.4%, P=0.012), but only the biases in hemoglobin, hematocrit, albumin, and total proteins exceeded the quality specifications for bias. Compared to when sitting or supine, standing patients had significantly higher levels of hemoglobin (4.8%, P<0.001 and 7.1%, P<0.001, respectively), hematocrit (5.3%, P<0.001 and 6.9%, P<0.001, respectively), albumin (6.4%, P<0.001 and 10.3%, P<0.001, respectively), ALP (7.8%, P<0.001 and 11.1%, P<0.001, respectively), ALT (8.3%, P<0.001 and 9.1%, P<0.001, respectively), amylase (6.3%, P<0.001 and 8.7%, P<0.001, respectively), AST (5.6%, P=0.003 and 11.1%, P<0.001, respectively), conjugated bilirubin (6.2%, P=0.003 and 7.2%, P<0.001, respectively), total bilirubin (12.0%, P=0.001 and 13.3%, P<0.001, respectively), calcium (3.1%, P<0.001 and 3.4%, P<0.001, respectively), HDL cholesterol (5.7%, P<0.001 and 9.7%, P<0.001, respectively), total cholesterol (5.7%, P<0.001 and 8.9 %, P<0.001, respectively), CK (5.3%, P<0.001 and 8.0%, P<0.001, respectively), creatinine (1.4%, P=0.028 and 1.9 %, P=0.016, respectively), GGT (9.5%, P=0.002 and 11.1%, P<0.001, respectively), glucose(3.8%, P=0.022 and 5.4%, P=0.001, respectively), iron (5.2%, P=0.015 and 7.0%, P=0.002, respectively), LDH (7.2%, P=0.001 and 9.8 %, P<0.001, respectively), lipase (4.0%, P=0.004 and 3.4%, P=0.016, respectively), magnesium (P=0.197 and 3.5%, P<0.001, respectively), total protein (8.0%, P<0.001 and 10.7%, P<0.001, respectively), and triglycerides(6.6%, P=0.002 and 11.5%, P<0.001, respectively), and significantly lower levels of urea (-1.9%, P=0.005 and -3.1%, P<0.001, respectively). However, when compared to the quality specifications for bias, the differences in hemoglobin, hematocrit, albumin, ALP, total bilirubin, calcium, total and HDL cholesterol, glucose, LDH, and total protein between sitting or supine and standing were considered meaningful. Additionally, the difference in levels of amylase, AST, GGT, magnesium, and triglycerides between supine and standing were considered meaningful. Levels of chloride, CRP, phosphate, sodium, potassium, and uric acid levels were not affected by patient posture.

   Biospecimens

   • Bodily Fluid - Plasma
   • Bodily Fluid - Blood
   • Bodily Fluid - Serum

   Preservative Types

   • None (Fresh)

   Diagnoses:

   • Normal

   Platform:

   Analyte	Technology Platform
   Carbohydrate	Clinical chemistry/auto analyzer
   Electrolyte/Metal	Clinical chemistry/auto analyzer
   Cell count/volume	Clinical chemistry/auto analyzer
   Steroid	Clinical chemistry/auto analyzer
   Protein	Clinical chemistry/auto analyzer
   Small molecule	Clinical chemistry/auto analyzer
   Lipid	Clinical chemistry/auto analyzer

   Pre-analytical Factors:

   Classification	Pre-analytical Factor	Value(s)
   Biospecimen Acquisition	Patient posture	Sitting Standing Supine
   Biospecimen Aliquots and Components	Aliquot sequential collection	1st collection 2nd collection 3rd collection
   Preaquisition	Patient body mass index	Mean height 1.68 ± 0.11 m and Mean weight 68 ± 12 kg
   Preaquisition	Patient age	44±11 years
   Preaquisition	Patient gender	Female Male

   View more