Blood loss from laboratory diagnostic tests in children

Excessive diagnostic phlebotomy in children and critically ill patients is a frequent phenomenon in many hospitals. However, little attention is paid to a single blood volume taken routinely everyday from thousands of patients worldwide. The objective of the present study was to assess the volume of a single blood sample draw for laboratory testing in a pediatric population in relation to child age and weight, number of diagnostic tests requested by physicians, laboratory needs, and size of collection tube.

A single blood volume draw for diagnostic tests was measured in 3136 consecutive routine samples taken from children (from 1 day to 18 years old) and placed into a Microvette® or regular sampling tubes. The serum excess was calculated by taking into account the serum volume needed for the requested number of tests and the dead volume of analyzer.

A huge variation in blood volume draws between individual patients, regardless of the number of tests requested, has been observed. The number of blood samples placed into the microvette decreased with patients' age, with 53.9% in children younger than 1 month old and 9.3% in children older than 12 years old. There was a clear-cut increase in the mean value of the blood volume draw with an increase in children's age. Only 2% of children up to 3 years old had a blood volume draw >1 mL/kg body weight.

Each pediatric laboratory should have a clear-cut recommendation on the amount on blood volume necessary for the requested number of tests.