Ensuring quality has become a daily requirement in laboratories. In haemostasis, even more than in other disciplines of biology, quality is determined by a pre-analytical step that encompasses all procedures, starting with the formulation of the medical question, and includes patient preparation, sample collection, handling, transportation, processing, and storage until time of analysis. This step, based on a variety of manual activities, is the most vulnerable part of the total testing process and is a major component of the reliability and validity of results in haemostasis and constitutes the most important source of erroneous or un-interpretable results. Pre-analytical errors may occur throughout the testing process and arise from unsuitable, inappropriate or wrongly handled procedures. Problems may arise during the collection of blood specimens such as misidentification of the sample, use of inadequate devices or needles, incorrect order of draw, prolonged tourniquet placing, unsuccessful attempts to locate the vein, incorrect use of additive tubes, collection of unsuitable samples for quality or quantity, inappropriate mixing of a sample, etc. Some factors can alter the result of a sample constituent after collection during transportation, preparation and storage. Laboratory errors can often have serious adverse consequences. Lack of standardized procedures for sample collection accounts for most of the errors encountered within the total testing process. They can also have clinical consequences as well as a significant impact on patient care, especially those related to specialized tests as these are often considered as “diagnostic”. Controlling pre-analytical variables is critical since this has a direct influence on the quality of results and on their clinical reliability. The accurate standardization of the pre-analytical phase is of pivotal importance for achieving reliable results of coagulation tests and should reduce the side effects of the influence factors. This review is a summary of the most important recommendations regarding the importance of pre-analytical factors for coagulation testing and should be a tool to increase awareness about the importance of pre-analytical factors for coagulation testing.

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Pre-analytical issues in the haemostasis laboratory: guidance for the clinical laboratories

Preoperative Hemostasis Testing The united Kingdom national institute for Health and Care Excellence (niCE) recommends consideration of laboratory tests of hemostasis in selected patients undergoing moderate or severe surgery and with an American Society of Anesthesiologists (ASA) physical status classification system score of 3 or 4.1 The guideline specifically states to consider preoperative hemostasis testing in patients with chronic liver disease and ASA score of 3 or 4. The Practice Advisory for Preanesthesia Evaluation by the ASA2 states that “clinical characteristics to consider for ordering selected coagulation studies include bleeding disorders, renal dysfunction, liver dysfunction, and type and invasiveness of procedure.” routine preoperative hemostasis testing may include platelet count, prothrombin time (PT), activated partial thromboplastin time (aPTT), and fibrinogen levels, although the niCE guidelines specifically refer to PT and aPTT testing only. Patients with liver diseases frequently have abnormal routine diagnostic tests of hemostasis. it has long been a “common practice” to attempt to correct these abnormalities by transfusion of blood products before invasive procedures, but recent insights in the hemostatic status of patients with liver disease cast doubt on this policy.3 Specifically, routine laboratory values in patients with liver disease may not accurately reflect the hemostatic status of these patients,4,5 and there is little evidence that routine preoperative hemostasis tests predict the risk for procedural bleeding in patients with liver disease.6–8 in this commentary, we provide evidence that, in contrast to what is suggested by the niCE and ASA guidelines, the role of preoperative hemostasis screening for any patient with liver disease undergoing surgery is limited, which has important consequences for perioperative hemostatic management.

Value of Preoperative Hemostasis Testing in Patients with Liver Disease for Perioperative Hemostatic Management

To examine the benefit of determination of the bleeding time as a preoperative screening test, the medical records of all patients who had a prolonged bleeding time during a six-month period were reviewed. At Northwestern Memorial Hospital, where the bleeding time test is part of the presurgical panel, 1,941 bleeding time determinations were performed during six months. Prolonged bleeding times were recorded in 110 preoperative patients, of whom 83 (75 percent) had bleeding risk factors, including drug ingestion, thrombocytopenia, and azotemia. In these patients, the bleeding time ranged unpredictably from 10 to more than 20 minutes. However, of the 27 patients without apparent risk factors, only two had bleeding times of more than 20 minutes. This small number probably does not justify the routine use of the test in all preoperative patients. Rather, the test should be used selectively for those subjects who, on the basis of history or laboratory evidence, are suspected of being at risk of hemorrhage. Moreover, even in these patients, prolongation of the bleeding time may not always be associated with excessive surgical blood loss.

The Bleeding Time as a Preoperative Screening Test

Background Patients with mild bleeding disorders are at risk of perioperative bleeding, but screening for these disorders remains challenging. Objectives We aimed to assess the prevalence of hemostatic abnormalities in patients with and without reported bleeding symptoms on a preoperative questionnaire, consisting of guideline-proposed questions, and appraised the diagnostic value of several screening modalities for the identification of patients with hemostatic abnormalities. Methods In this observational study, 240 patients with and 95 patients without bleeding symptoms on the preoperative questionnaire were included. Patients with known bleeding disorders, antithrombotic drugs, thrombocytopenia, and anemia were excluded. Preoperatively, all patients underwent elaborate hemostatic testing. Hemostatic abnormalities were defined as coagulation, vWF, or fibrinolysis factor levels below reference range and platelet function defects. Screening modalities included the ISTH Bleeding Assessment Tool (ISTH-BAT), PT, aPTT, TT, Euglobulin Lysis Time (ELT), and Platelet Function Analyser (PFA). Results In 21 of 240 (8.8%) patients reporting bleeding symptoms, hemostatic abnormalities were found, including 7 reduced coagulation factor levels, 10 platelet function abnormalities, and 4 reduced vWF levels. In comparison, 10 of 95 (10.5%) patients not reporting bleeding symptoms had abnormalities. The ISTH-BAT could not identify patients with abnormalities, while PT, aPTT, TT, ELT, and PFA had high specificity but low sensitivity to detect abnormalities. Conclusions The prevalence of hemostatic abnormalities in both patients with and without reported bleeding symptoms was 9%-10%. This suggests that the guideline-based questionnaire cannot differentiate between patients with and without abnormalities, while the discriminative power of the screening modalities is also limited.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/rth2.12114

Preoperative screening for bleeding disorders: A comprehensive laboratory assessment of clinical practice.

Purpose
Current recommendations for the assessment of the risk of perioperative bleeding limit coagulation testing to patients with a personal and/or family history of bleeding. As no simple preoperative screening questionnaire is currently available, we assessed the performance of a novel screening questionnaire for its ability to detect bleeding disorders.

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Preoperative hemostatic assessment: a new and simple bleeding questionnaire

Recently the French Society of Anaesthesia and Intensive Care (Societe Francaise d'Anesthesie et de Reanimation [SFAR]) issued recommendations for the prescription of routine preoperative testing before a surgical or non-surgical procedure, requiring any type of anaesthesia. Thirty clinical specialists performed a systematic analysis of the literature, and recommendations were then developed using the GRADE (Grading of Recommendations Assessment, Development and Evaluation) system. One part of these guidelines is dedicated to haemostatic assessment. The goal of pre-anaesthetic screening for congenital or acquired haemostatic disorders is to prevent perioperative haemorrhagic complications through appropriate medical and surgical management. Preoperative assessment of bleeding risk requires a detailed patient interview to determine any personal or family history of haemorrhagic diathesis, and a physical examination is necessary in order to detect signs of coagulopathy. Laboratory investigation of haemostasis should be prescribed, not systematically, but depending on clinical evaluation and patient history. Standard tests (prothrombin time, activated partial thromboplastin time, platelet count) have a low positive predictive value for bleeding risk in the general population. Patients with no history of haemorrhagic diathesis and no conditions liable to interfere with haemostasis should not undergo pre-interventional haemostasis testing. Conversely, the existence of a positive history or a disease that could interfere with haemostasis should be an indication for clinically appropriate testing.

Serge Molliex

Papers

Pre-interventional haemostatic assessment: Guidelines from the French Society of Anaesthesia and Intensive Care.