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Cytological and Biomolecular Measuring Procedures

Working Group 8.32


Gravimetrically controlled dilution of blood

The working group develops reference measurement procedures to determine blood cell concentrations. These are used in ring trials for the complete blood count to determine reference measurement values. This serves the external quality assurance of haematological laboratories as prescribed according to the Directive of the German Medical Association (RiliBÄK). For cell concentration measurement the blood sample is diluted with gravimetric control and then measured with a so called flow cytometer.

Flow cytometers count cells during passage of an orifice (electric measurement of a change in impedance) or passage through a laser beam (optical measurement of light scattering or fluorescence). The amount of sample is measured with a balance or using precision volumetric dosage systems developed by PTB. In this way the concentration of erythrocytes, leukocytes and platelets is determined.

The complete blood count also covers determination of the haemoglobin concentration. For this purpose all variants of haemoglobin are chemically transformed into a stable compound to determine the concentration at a proper dilution using a spectrophotometer.


Kammel, M.; Kummrow, A.; Neukammer, J.
Reference measurement procedures for the accurate determination of cell concentrations: present status and future developments
Opens external link in new windowJ. Lab. Med. 36 (2012) 25-34.

Reitz, S.; Kummrow, A.; Kammel, M.; Neukammer, J.
Determination of micro-litre volumes with high accuracy for flow cytometric blood cell counting
Opens external link in new windowMeas. Sci. Technol. 21 (2010), 074006.

Establishing traceability of photometric absorbance values for accurate measurements of the haemoglobin concentration in blood
Opens external link in new windowMetrologia 50 (2013) 539-548.

Measurands of the complete blood count

The parameters or derived quantities marked with * are referred to as erythrocyte indices and are calculated from the concentration of the red blood cells, the haemoglobin concentration and the haematocrit value. The symbols and formula symbols are based on DIN 58932-2.


Andreas Kummrow, Jörg Neukammer 8.01