Spurious hyperglycaemia impairs automated leucocyte counting. A pilot study with two different haematological analysers.

Pre-analytical errors are a frequent problem that can compromise the quality of the total testing process and, along with analytical mistakes, can have a negative impact on the reliability of test results and patients’ safety1. There is now consolidated evidence that the vast majority of pre-analytical problems emerge from mishandling or scarcely standardised procedures during collection, management and preparation of biological specimens2. In particular, sample contamination by exogenous fluids (e.g., saline) or therapeutics (e.g., antibiotics, thrombolytic agents, glucose or potassium solutions) is a frequent source of problems in diagnostic testing, wherein test values may be variably biased by dilution or direct interference from the specific contaminating substance3. A paradigmatic example is contamination of biological samples with glucose-containing solutions. The administration of intravenous standard glucose solutions, typically 5% (i.e., 278 mmol/L) dextrose in water, is commonplace in clinical practice not only for the treatment of hypoglycaemia, but also for maintaining tissue hydration after acute disease or surgery, and as a means of parenteral nutrition4. Although it has been recommended that blood samples should be drawn from the opposite arm from which glucose solutions and other intravenous fluids are administered5, blood samples are frequently collected from infusion routes, in order to avoid a second venipuncture and save precious time in short stay or critical wards such as emergency departments and intensive care units. Even the best practice of the Clinical and Laboratory Standards Institute for collecting blood from intravenous lines, that is clearance of fluid before the sample is collected by discarding an adequate amount of fluid (i.e., typically 5 mL or 6 times the dead space volume)6, is frequently overlooked. Therefore, blood sample contamination is a relatively common occurrence and may lead to diagnostic errors and adverse consequences for patients’ health, including inappropriate therapeutic correction of spurious abnormalities (e.g., hypoglycaemia or hyperkalaemia), as well as unjustified transfusion of blood components in the case of spurious dilution of blood7,8.It has been previously shown that blood sample contamination by glucose solutions may generate a significant bias in clinical chemistry9 and coagulation testing10. Nevertheless, to the best of our knowledge, no information exists on the effect of spurious hyperglycaemia on leucocyte counts and differential. This is of paramount importance, since biased results may confound diagnostic reasoning and lead to inappropriate therapeutic decisions. The aim of this study was, therefore, to evaluate whether contamination of whole blood samples with standard glucose solutions (as may occur during normal venipuncture contaminated by exogenous glucose) may affect leucocyte counts measured by two widely used haematological analysers (ADVIA 2120 [Siemens Diagnostic Solutions, Milan, Italy] and XE-2100 [Dasit SpA, Cornaredo, Italy]), characterised by different analytical technologies.