Table 2. Preanalytical bias of routine venipuncture.

Venipuncture factor	Needle gauge	Needle type	Toruniquet application		Body positioning
Lab parameter	23 G vs. 21 G	Winged vs. regular	1 minute	3 minute	Sitting vs. lying
Clinical chemistry	negligible	negligible	Albumin (+1.58%; ±1.3%) Calcium (+1.6%; ±0.8%) Chloride (-0.5%; ±0.5%) Potassium (-2.8%; ±1.8%)	ALT (+15.7%; ±12.0%) Albumin (+8.6%; ±1.3%) Calcium (+3.6%; ±0.8%) Chloride (-1.1%; ±0.5%) Cholesterol (+9.1%; ±4.0%) Glucose (-3.7%; ±2.2%) Iron (+8.8%; ±8.8%) Potassium (-4.8%; ±1.8%)	Albumin (+2.0%; ±1.4%) Protein (+2.9%; ±1.4%)
Platelets and coagulation	negligible	negligible	negligible	PT/INR (-3.1%; ±2.0%) Fibrinogen (+10.1%; ±4.8%)	n.a.
Haematology	n.a.	negligible	WBC (-6.7%; ±5.6%) RBC (+3.6%; ±1.7%) Haemoglobin (+3.0%; ±1.8%) Haematocrit (+3.7%; ±1.7%) Lymphocytes (-7.9%; ±7.4%) Monocytes (-14.4%; ±13.2%)	WBC (-10.1%; ±5.6%) RBC (+7.4%; ±1.7%) Haemoglobin (+6.2 ; ±1.8%) Haematocrit (+7.3%; ±1.7%) Lymphocytes (-10.7%; ±7.4%) Monocytes (-22.0%; ±13.2%)	Haemoglobin (+2.3%; ±1.8%) Haematocrit (+1.7%; ±1.7%)

Data in brackets are the actual and desirable bias respectively; “n.a.” indicates factors for which bias was not measured regardless to a significant effect may exist.