Abnormal gel flotation caused by contrast media during adrenal vein sampling

Clot activators and anticoagulant additives for blood collection. A critical review on behalf of COLABIOCLI WG-PRE-LATAM

In the clinical laboratory, knowledge of and the correct use of clot activators and anticoagulant additives are critical to preserve and maintain samples in optimal conditions prior to analysis. In 2017, the Latin America Confederation of Clinical Biochemistry (COLABIOCLI) commissioned the Latin American Working Group for Preanalytical Phase (WG-PRE-LATAM) to study preanalytical variability and establish guidelines for preanalytical procedures to be applied by clinical laboratories and health care professionals. The aim of this critical review, on behalf of COLABIOCLI WG-PRE-LATAM, is to provide information to understand the mechanisms of the interactions and reactions that occur between blood and clot activators and anticoagulant additives inside evacuated tubes used for laboratory testing. Clot activators - glass, silica, kaolin, bentonite, and diatomaceous earth - work by surface dependent mechanism whereas extrinsic biomolecules - thrombin, snake venoms, ellagic acid, and thromboplastin - start in vitro coagulation when added to blood. Few manufacturers of evacuated tubes state the type and concentration of clot activators used in their products. With respect to anticoagulant additives, sodium citrate and oxalate complex free calcium and ethylenediaminetetraacetic acid chelates calcium. Heparin potentiates antithrombin and hirudin binds to active thrombin, inactivating the thrombin irreversibly. Blood collection tubes have improved continually over the years, from the glass tubes containing clot activators or anticoagulant additives that were prepared by laboratory personnel to the current standardized evacuated systems that permit more precise blood/additive ratios. Each clot activator and anticoagulant additive demonstrates specific functionality, and both manufacturers of tubes and laboratory professional strive to provide suitable interference-free sample matrices for laboratory testing. Both manufacturers of in vitro diagnostic devices and laboratory professionals need to understand all aspects of venous blood sampling so that they do not underestimate the impact of tube additives on laboratory testing.

Causes of Preanalytical Interferences on Laboratory Immunoassays - A Critical Review

The immunoassays methods need avoiding interferences that can influence result interpretation. Main sources of interference arise from either patient status, preparation and physiology or laboratory process and procedures. The aim of this non-systematic critical review is to highlight the preanalytical interferences on laboratory immunoassays. Blood hormone profile changes according with age and depending on sex: these are important variables, mainly in newborn, during both sexual maturation and childbearing. Gonadotropins FSH and LH show a sharp increase with age in females, whereas in males LH appears rather stable. With age both males and females show progressive decay of the hormone profile. Stress causes variations, as it influences GH, prolactin, Cortisol and the total/free ratio of thyroid hormone. Diurnal variations, day of cycle, influence by estrogens on thyroid hormone are relevant for result variability. Paraproteins and autoantibodies can interfere in some assays particularly drug, vitamin D and thyroid hormone. As regards the variables due to sample matrix, and to evacuated tubes components, some additives and anticoagulants have been reported to influence specific assays, e.g. thyroid hormone. Hemolysis, lipemia and bilirubin cause interferences on specific techniques/tests, e.g. ferritin, TSH, Vitamin B12, progesterone and folic acid. Nicotine and cocaine addictions interfere with some hormones. Thus, laboratory professionals should be aware of preanalytical problems particularly important when dealing with the immunoassays, by taking appropriate actions to avoid any relevant interferences.

Sample management for clinical biochemistry assays: Are serum and plasma interchangeable specimens?

The constrained economic context leads laboratories to centralize their routine analyses on high-throughput platforms, to which blood collection tubes are sent from peripheral sampling sites that are sometimes distantly located. Providing biochemistry results as quickly as possible implies to consolidate the maximum number of tests on a minimum number of blood collection tubes, mainly serum tubes and/or tubes with anticoagulants. However, depending on the parameters and their pre-analytical conditions, the type of matrix - serum or plasma - may have a significant impact on results, which is often unknown or underestimated in clinical practice. Importantly, the matrix-related effects may be a limit to the consolidation of analyses on a single tube, and thus must be known by laboratory professionals. The purpose of the present critical review is to put forward the main differences between using serum and plasma samples on clinical biochemistry analyses, in order to sensitize laboratory managers to the need for standardization. To enrich the debate, we also provide an additional comparison of serum and plasma concentrations for approximately 30 biochemistry parameters. Properties, advantages, and disadvantages of serum and plasma are discussed from a pre-analytical standpoint - before, during, and after centrifugation - with an emphasis on the importance of temperature, delay, and transport conditions. Then, differences in results between these matrices are addressed for many classes of biochemistry markers, particularly proteins, enzymes, electrolytes, lipids, circulating nucleic acids, metabolomics markers, and therapeutic drugs. Finally, important key-points are proposed to help others choose the best sample matrix and guarantee quality of clinical biochemistry assays. Moreover, awareness of the implications of using serum and plasma samples on various parameters assayed in the laboratory is an important requirement to ensure reliable results and improve patient care.