Preanalytical variables and factors that interfere with the biochemical parameters: a review

Introduction The total testing process, which begins with the order of the physician, includes the preanalytical, analytical and postanalytical phases and ends with the results ready for interpretation. To obtain a reliable test result requires detection of all steps however, to control the preanalytical stage is such a complex way that much of the steps are human dependent and out of the laboratory’s control thus occupies the most erroneous part of the total testing. The worst side is that the error in that stage often becomes apparent in the analytical or postanalytical phase. The aim is to highlight the multifactorial human dependent erroneous stage that affects the biochemical routine test results, which can be easily prevented with awareness and laboratory staff education. We will concentrate on the preanalytical errors which include specimen type selection, blood collection, blood collection equipments and the factors interfering with biochemical tests. Conclusion The quality of the analytical phase increased due to the interest, tight control and following the quality procedures both internal and external established by the medical laboratories and manufacturers. Introduction The total testing process includes the preanalytical, analytical and postanalytical phases which begins with the order of the physician and ends with the result ready for interpretation. With the improvements in the analytical phase by focusing on the analytical quality, the error magnitude decreased, thus the preanalytical stage constituted the most error-prone part with a percentage of 46–711,2. The preanalytical stage is so complex that a mistake at any step often becomes apparent in the analytical or postanalytical phase. The error magnitude increases especially in the human dependent parts, e.g. sample collection, handling, transportation, storage which are mostly out of the laboratory’s control. With the increasing number in laboratory tests per patients, the burden of phlebotomy increased3. In this review we will concentrate on the preventable preanalytical errors which include specimen type selection, blood collection, blood collection equipments and the factors interfering biochemical tests. Better control of these variables will improve the total analysis quality for which the big role in the play is given to the laboratories by the accreditation agencies4,5. Blood collection errors Because blood exerts the physiological states of the body systems, much emphasis has been placed on analysing blood samples. • Venipuncture: intravenous access for blood collection, also named as phlebotomy, is commonly performed from the median cubital vein. A good phlebotomy technique performed has to minimise trauma to the patient, reduce the risk of recollection and minimise the risk of haemolysis. The phlebotomy errors are detected to cause 24%–30% of a serious patient misdiagnosis4. • During blood collection, the arm has to be positioned downward to avoid possible backflow of additives (EDTA, heparin, etc.) because of the vacuum inside the tube. The phlebotomy site with a running IV has to be avoided, however if there is no alternative for exp. because of mastectomy, hematoma, or infection, the distal site of the IV has to be preferred. • Cleaning the venipuncture site: the site for venipuncture is to be cleaned with 70% ethanol. Attention is needed for ethanol to be dried before the needle is inserted into the vein otherwise alcohol causes erythrocyte membrane rupture and subsequent haemolysis thus the interferences. Samples for blood culture should be collected after cleaning the selected site with povidone–iodine. • Tourniquet application: the tourniquet should be released once the first blood flow was established. More than 1 min of tourniquet left results in haemoconcentration occurrence and test errors6. Haemoconcentration causes increases in serum calcium and potassium7. Clenching fist causes elevation in serum CK and potassium. • Needle or syringe: syringe usage in venipuncture is a major cause of in vitro haemolysis due to the force applied during aspiration and transfer into the tube. The vacuum inside the tube is predetermined to collect appropriate volume of blood into tubes. However, performing venipuncture with a syringe and further aliquoting the blood from syringe often result with a small volume of blood in the tube when multiple types of specimens are needed. * Corresponding author Email: [email protected] Department of Clinical Chemistry, Katip Çelebi University, Ataturk Training and Research Hospital, Izmir, Turkey