Joint EFLM-COLABIOCLI Recommendation for venous blood sampling

This document provides a joint recommendation for venous blood sampling of the European Federation of Clinical Chemistry and Laboratory Medicine (EFLM) Working Group for Preanalytical Phase (WG-PRE) and Latin American Working Group for Preanalytical Phase (WG-PRE-LATAM) of the Latin America Confederation of Clinical Biochemistry (COLABIOCLI). It offers guidance on the requirements for ensuring that blood collection is a safe and patient-centered procedure and provides practical guidance on how to successfully overcome potential barriers and obstacles to its widespread implementation. The target audience for this recommendation are healthcare staff members directly involved in blood collection. This recommendation applies to the use of a closed blood collection system and does not provide guidance for the blood collection with an open needle and syringe and catheter collections. Moreover, this document neither addresses patient consent, test ordering, sample handling and transport nor collection from children and unconscious patients. The recommended procedure is based on the best available evidence. Each step was graded using a system that scores the quality of the evidence and the strength of the recommendation. The process of grading was done at several face-to-face meetings involving the same mixture of stakeholders stated previously. The main parts of this recommendation are: 1) Pre-sampling procedures, 2) Sampling procedure, 3) Post-sampling procedures and 4) Implementation. A first draft of the recommendation was circulated to EFLM members for public consultation. WG-PRE-LATAM was also invited to comment the document. A revised version has been sent for voting on to all EFLM and COLABIOCLI members and has been officially endorsed by 33/40 EFLM and 21/21 COLABIOCLI members. We encourage professionals throughout Europe and Latin America to adopt and implement this recommendation to improve the quality of blood collection practices and increase patient and workers safety.

Impact of blood cell counts and volumes on glucose concentration in uncentrifuged serum and lithium-heparin blood tubes

BACKGROUND

Although it is known that glucose concentration exhibits a time-dependent decay in uncentrifuged serum and lithium-heparin blood tubes, no evidence exists on how this variation may depend on blood cell counts (CBC) and volumes.

METHODS

Venous blood was drawn from 30 non fasting healthy volunteers into three serum and three lithium-heparin tubes. One serum and lithium-heparin tubes were centrifuged within 15 min after collection and glucose was measured with a hexokinase assay. The second and third serum and lithium-heparin tubes were maintained at room temperature for 1 and 2 h after the first tubes were centrifuged. These other tubes were then centrifuged and glucose was measured. CBC was performed in the first lithium-heparin tube, before centrifugation.

RESULTS

The mean decrease of glucose was higher in lithium-heparin plasma than in serum (0.33 vs. 0.24 mmol/L/h; p<0.001). Glucose concentration decreased by 7% and 5% per hour in lithium-heparin plasma and serum, respectively. In univariate analysis, the absolute decrease of glucose concentration was associated with sex (higher in men than in women), red blood cell (RBC) count, hematocrit, white blood cell (WBC) count, neutrophils and monocytes in both lithium-heparin plasma and serum. In multivariate analysis, the decrease of glucose concentration remained independently associated with RBC, WBC, neutrophils and monocytes in both sample matrices. No significant association was found with platelet number and erythrocyte or platelet volume.

CONCLUSIONS

Glucose concentration decrease in uncentrifuged lithium-heparin and serum tubes depends on the baseline number of RBC, WBC, neutrophils and monocytes within the tubes.

European survey on preanalytical sample handling - Part 2: Practices of European laboratories on monitoring and processing haemolytic, icteric and lipemic samples. On behalf of the European Federation of Clinical Chemistry and Laboratory Medicine (EFLM) Working Group for the Preanalytical Phase (WG-PRE)

Introduction

No guideline currently exists on how to detect or document haemolysis, icterus or lipemia (HIL) in blood samples, nor on subsequent use of this information. The EFLM WG-PRE has performed a survey for assessing current practices of European laboratories in HIL monitoring. This second part of two coherent articles is focused on HIL.

Materials and methods

An online survey, containing 39 questions on preanalytical issues, was disseminated among EFLM member countries. Seventeen questions exclusively focused on assessment, management and follow-up actions of HIL in routine blood samples.

Results

Overall, 1405 valid responses from 37 countries were received. A total of 1160 (86%) of all responders stating to analyse blood samples - monitored HIL. HIL was mostly checked in clinical chemistry samples and less frequently in those received for coagulation, therapeutic drug monitoring and serology/infectious disease testing. HIL detection by automatic HIL indices or visual inspection, along with haemolysis cut-offs definition, varied widely among responders. A quarter of responders performing automated HIL checks used internal quality controls. In haemolytic/icteric/lipemic samples, most responders (70%) only rejected HIL-sensitive parameters, whilst about 20% released all test results with general comments. Other responders did not analysed but rejected the entire sample, while some released all tests, without comments. Overall, 26% responders who monitored HIL were using this information for monitoring phlebotomy or sample transport quality.

Conclusion

Strategies for monitoring and treating haemolytic, icteric or lipemic samples are quite heterogeneous in Europe. The WG-PRE will use these insights for developing and providing recommendations aimed at harmonizing strategies across Europe.

European survey on preanalytical sample handling - Part 1: How do European laboratories monitor the preanalytical phase? On behalf of the European Federation of Clinical Chemistry and Laboratory Medicine (EFLM) Working Group for the Preanalytical Phase (WG-PRE)

Introduction

Compared to other activities of the testing process, the preanalytical phase is plagued by a lower degree of standardization, which makes it more vulnerable to errors. With the aim of providing guidelines and recommendations, the EFLM WG-PRE issued a survey across European medical laboratories, to gather information on local preanalytical practices. This is part one of two coherent articles, which covers all practices on monitoring preanalytical quality except haemolysis, icterus and lipemia (HIL).

Materials and methods

An online survey, containing 39 questions dealing with a broad spectrum of preanalytical issues, was disseminated to EFLM member countries. The survey included questions on willingness of laboratories to engage in preanalytical issues.

Results

Overall, 1405 valid responses were received from 37 countries. 1265 (94%) responders declared to monitor preanalytical errors. Assessment, documentation and further use of this information varied widely among respondents and partially among countries. Many responders were interested in a preanalytical online platform, holding information on various aspects of the preanalytical phase (N = 1177; 87%), in a guideline for measurement and evaluation of preanalytical variables (N = 1235; 92%), and in preanalytical e-learning programs or webinars (N = 1125; 84%). Fewer responders were interested in, or already participating in, preanalytical EQA programs (N = 951; 71%).

Conclusion

Although substantial heterogeneity was found across European laboratories on preanalytical phase monitoring, the interest in preanalytical issues was high. A large majority of participants indicated an interest in new guidelines regarding preanalytical variables and learning activities. This important data will be used by the WG-PRE for providing recommendations on the most critical issues.

Genetic and lifestyle predictors of ischemic stroke severity and outcome

BACKGROUND

Different models that include clinical variables and blood markers have been investigated to predict acute ischemic stroke treatment course and recovery.

AIM

The aim of the study was to investigate associations between lipid levels, lifestyle factors, hemostatic (F5, F2, SERPINE1, F13A1, and FGB), and atherogenic (APOA5 and ACE) gene variants and acute ischemic stroke (AIS) severity.

MATERIALS AND METHODS

This study included 250 patients with AIS in which F5, F2, SERPINE1, F13A1, FGB, APOA5, and ACE genotypes were determined. Total cholesterol (TC), high-density cholesterol, low-density cholesterol, and triglycerides concentrations were measured within 24 h of the AIS onset. Examination of the neurological deficit was done using National Institutes of Health Stroke Scale/Score (NIHSS).

RESULTS

APOA5 genotype [TC + CC] was more frequent (P = 0.026) in patients with the NIHSS score ≥ 21. Univariate regression analysis has shown that triglycerides (OR 0.55, 95% CI 0.34-0.91; P = 0.019), obesity (0.28, 95% CI 0.10-0.73; P = 0.010), age (OR 1.08, 95% CI 1.04-1.13; P < 0.001), and APOA5 genotype (TC + CC) (OR 2.40, 95% CI 1.10-5.25; P = 0.034) are significantly associated with a severe stroke. When all variables were included in model age (OR 1.06, 95% CI 1.01-1.11; P = 0.018), obesity (OR 0.25, 95% CI 0.08-0.77; P = 0.016) and APOA5 genotype (TC + CC) (OR 3.26, 95% CI 1.29-8.23; P = 0.012) remained significant for the risk of severe AIS.

CONCLUSION

APOA5 genotype (TC + CC), age, and obesity could be used as prognostic risk factors for a very severe stroke (NIHSS ≥ 21).

Managing inappropriate utilization of laboratory resources

Background The inappropriate use of laboratory resources, due to excessive number of tests not really necessary for patient care or by failure to order the appropriate diagnostic test, may lead to wrong, missed or delayed diagnosis, thus potentially jeopardizing patient safety. It is estimated that 5-95% of tests are currently used inappropriately, depending on the appropriateness criteria, thus significantly contributing to the potential of generating medical errors, the third leading cause of death in the US. Content In this review, we discuss the reasons as well as the medical and financial consequences of inappropriate utilization of laboratory tests. We then provide demand management (DM) tools as a means for overcoming this issue and also discuss their benefits, challenges, limitations and requirements for successful implementation. Summary and outlook When based on current evidence, adapted to local conditions and developed in close collaboration with clinicians, DM is a reasonable strategy for progressing toward better management of over- and underuse of laboratory resources.

Blood sample quality

Several lines of evidence now confirm that the vast majority of errors in laboratory medicine occur in the extra-analytical phases of the total testing processing, especially in the preanalytical phase. Most importantly, the collection of unsuitable specimens for testing (either due to inappropriate volume or quality) is by far the most frequent source of all laboratory errors, thus calling for urgent strategies for improving blood sample quality and managing data potentially generated measuring unsuitable specimens. A comprehensive overview of scientific literature leads us to conclude that hemolyzed samples are the most frequent cause of specimen non-conformity in clinical laboratories (40-70%), followed by insufficient or inappropriate sample volume (10-20%), biological samples collected in the wrong container (5-15%) and undue clotting (5-10%). Less frequent causes of impaired sample quality include contamination by infusion fluids (i.e. most often saline or glucose solutions), cross-contamination of blood tubes additives, inappropriate sample storage conditions or repeated freezing-thawing cycles. Therefore, this article is aimed to summarize the current evidence about the most frequent types of unsuitable blood samples, along with tentative recommendations on how to prevent or manage these preanalytical non-conformities.

Haemolysis and lipemia interfere with resistin and myeloperoxidase BioVendor ELISA assays

Introduction

The aim of our study was to investigate the influence of haemolysis and lipemia on resistin (RES) and myeloperoxidase (MPO) measurement by BioVendor enzyme-linked immunosorbent assays (ELISA).

Materials and methods

Blood was taken from healthy volunteers into lithium heparin tubes. Plasma samples were spiked with Lipofundin® emulsion (B. Braun Melsungen AG, Germany) for lipemia interference testing. Haemolysed samples were obtained by drawing aliquots of heparinized blood through a 26 gauge needle. Index of haemolysis (H), lipemia (L) and triglyceride concentration were measured on Abbott Architect c8000. Haemoglobin concentration was measured on Sysmex XN-1000. Concentrations of RES and MPO in all samples were determined with RES and MPO ELISA kits (BioVendor, Czech Republic). All measurements were performed in triplicate. Biases from the native samples were calculated for both analytes and compared with an arbitrary value (e.g. ± 10%).

Results

Triglyceride concentration in the investigated samples ranged from 0.57 to 38.23 mmol/L, which corresponds to L index from - 0.01 to 13.77. Haemoglobin concentration in all samples ranged from 0 to 8 g/L which correspond to H index from 0.05 to 8.77. Both MPO and RES showed significant biases at 1 g/L haemoglobin (58.7% and 66.7%, respectively). Also, both MPO and RES showed significant biases at 4.66 mmol/L triglycerides (33.8% and - 12.2%, respectively).

Conclusions

Resistin BioVendor assays are affected by haemolysis and lipemia already at low degree of interferent. Haemolysis was found to interfere at 1 g/L haemoglobin for both assays, while lipemia interferes at 4.66 mmol/L of triglycerides.

The diagnostic accuracy of clinical and laboratory parameters in the diagnosis of acute appendicitis in the adult emergency department population - a case control pilot study

Introduction

The evaluation of patients with suspected appendicitis strives to identify all patients with presenting symptoms while minimizing negative appendectomy rate. The aim of the study was to identify the optimal combination of clinical and laboratory parameters that should facilitate the emergency department surgeon’s definite decision.

Materials and methods

The study group comprised 120 patients with suspicion of acute appendicitis (AA). In 60 patients the AA diagnosis was confirmed intraoperatively and by histological analysis. Clinical parameters included: appetite, vomiting, diarrhea, dysuria, signs of localized peritonitis and pain migration. Measured laboratory parameters were: C-reactive protein (CRP), complete blood count (CBC) and the urine test strip.

Results

The control group of patients were more likely to present following symptoms: no changes in appetite (P < 0.001), diarrhea (P = 0.009) and dysuria (P = 0.047). CRP and white blood cell count (WBC) were significantly higher in the group with confirmed AA compared to the control group (44.7 vs. 6.6, and 13.6 ± 3.9 vs. 9.0 ± 3.4, respectively; P < 0.001). The multivariate logistic regression analysis identified lack of appetite (P = 0.013), absence of diarrhea (P = 0.004), and positive finding of signs of localized peritonitis (P = 0.013), as well as WBCs (P < 0.001) and negative urine test strip results (P = 0.009) as statistically significant predictors of AA. The highest percentage of correctly classified cases (82%) was achieved by combination of common clinical exam and basic inexpensive laboratory parameters (WBCs and urine test strip).

Conclusions

Acute appendicitis in the emergency setting may be successfully ruled in based on elevated WBCs and negative urine test strip in combination with signs of localized peritonitis, lack of appetite and absence of diarrhea. Since CRP did not contribute to the overall diagnostic accuracy, its use in AA diagnostic protocols is of no value.

Practical recommendations for managing hemolyzed samples in clinical chemistry testing

We suggest here a pragmatic approach for managing results of clinical chemistry testing in hemolyzed samples collected from adults/older children, attempting to balance the need to produce quality laboratory data with clinical urgency of releasing test results. Automatic measurement of the hemolysis index (H-index) in serum or plasma is highly advisable, whilst low-quality assessment of this test remains less good than a visual inspection. Regarding its practical use, when the H-index value does not generate an analytically significant bias, results can be released, whilst when the value is associated with analyte variation in a range between analytically and clinically significant bias (i.e. variation does not exceed the reference change value [RCV]), results of hemolysis-sensitive tests can be released in association with a comment describing the direction in which data are potentially altered, suggesting the need to collect another sample. When the H-index is associated with analyte variation exceeding clinically significant bias (i.e. variation exceeds the RCV), results of hemolysis-sensitive tests should be suppressed and replaced with a comment that biased results cannot be released because the sample is preanalytically compromised and advising the recollection of another sample. If H-index values reach an even higher critical cut-off (i.e. H-index corresponding to a cell-free hemoglobin concentration ≥10 g/L), all laboratory data may be unreliable and should hence be suppressed and replaced with a comment that all data cannot be released because the sample is grossly hemolyzed, also suggesting the recollection of another sample. Due to inaccuracy and imprecision, the use of corrective formulas for adjusting data of hemolysis-sensitive tests is discouraged.

Visual assessment of hemolysis affects patient safety

BACKGROUND

Manual handling of hemolyzed samples is not standardized and is vulnerable to errors. This study aimed to evaluate laboratory errors due to manual handling of hemolyzed samples and to assess the risk they might have for patient safety.

METHODS

Data were retrospectively obtained from a laboratory information system for 25 emergency tests from hemolyzed samples. Hemolysis (concentration of free hemoglobin >0.5 g/L) was visually assessed by comparison with a color chart. The reference person reestimated the routinely assessed degree of hemolysis to all samples (n=3185) received in the laboratory in a 1-week period. For each test, the correct and incorrect way of handling results was determined. Risk assessment was performed according to ISO 14971 standard with five categories of risk (S1-S5) and error occurrence (O1-O5).

RESULTS

In the studied period, the emergency laboratory received 495 hemolyzed samples (15.5%) with a total of 2518 laboratory test requests (15.5%): 102 (20.6%) of the reports from hemolyzed samples had a comment on hemolysis; 31% of the test results were handled incorrectly (20.7% due to the incorrect release of the test result despite hemolysis interference and 10.3% due to unnecessary suppression), accounting for 4.8% of the total test volume. Tests with the highest combination of risk and occurrence rate were troponin T, potassium and total bilirubin.

CONCLUSIONS

Manual handling of hemolyzed samples may lead to risk of errors in reporting results for troponin T, potassium and total bilirubin, which may have an effect on clinical decision. In addition, unnecessary suppression of the sample results unaffected by hemolysis could affect patient outcome.

Internal quality assurance of HIL indices on Roche Cobas c702

Automatic assessment of hemoglobin (H), lipaemia (L) and icterus (I) in serum or plasma (HIL indices) is the mainstay for evaluating sample quality. We planned this study to verify whether in-house prepared internal quality control (IQC) materials may be suitable for quality assurance of HIL indices. Pools containing different values of each of the three HIL indices were prepared from routine plasma samples, divided in aliquots and frozen at -20°C. Stability of frozen materials was assessed by thawing one aliquot of each pool after different days of freezing (1, 4, 8, 15, 22 and 29), and by measuring HIL indices on baseline fresh samples and frozen-thawed aliquots with Roche Cobas c702. Five fresh liquid IQCs materials were also measured at the same time points. Intra-assay and inter-assay imprecision of HIL indices calculated with commercial IQC materials ranged between 1.1-2.0% and 1.6-3.3%, respectively. When target values of HIL indices were calculated using frozen-thawed aliquots, the inter-assay imprecision of in-house prepared materials was optimal, even better than that of commercial liquid IQCs (H-index, 0.8% versus 1.6%; L-index, 2.2% versus 2.5%; I-index, 0.8% versus 3.3%). In conclusion, in-house prepared IQC materials are cost-effective alternatives to commercial liquid IQCs for HIL quality assurance.

Comparison of Enzymatic Assay for HBA1C Measurement (Abbott Architect) With Capillary Electrophoresis (Sebia Minicap Flex Piercing Analyser)

Objective

To compare the analytical performances of the enzymatic method (EM) and capillary electrophoresis (CE) for hemoglobin A1c (HbA1c) measurement.

Methods

Imprecision, carryover, stability, linearity, method comparison, and interferences were evaluated for HbA1c via EM (Abbott Laboratories, Inc) and CE (Sebia).

Results

Both methods have shown overall within-laboratory imprecision of less than 3% for International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) units (<2% National Glycohemoglobin Standardization Program [NGSP] units). Carryover effects were within acceptable criteria. The linearity of both methods has proven to be excellent (R2 = 0.999). Significant proportional and constant difference were found for EM, compared with CE, but were not clinically relevant (<5 mmol/mol; NGSP <0.5%). At the clinically relevant HbA1c concentration, stability observed with both methods was acceptable (bias, <3%). Triglyceride levels of 8.11 mmol per L or greater showed to interfere with EM and fetal hemoglobin (HbF) of 10.6% or greater with CE.

Conclusion

The enzymatic method proved to be comparable to the CE method in analytical performances; however, certain interferences can influence the measurements of each method.

Targeted Mass Spectrometry-Based Assays for Relative Quantification of 30 Brain-Related Proteins and Their Clinical Applications

Cerebrospinal fluid (CSF) is a promising clinical sample for identification of novel biomarkers for various neurological disorders. Considering its direct contact with brain tissue, CSF represents a valuable source of brain-related and brain-specific proteins. Multiple sclerosis is an inflammatory, demyelinating neurological disease affecting the central nervous system, and so far there are no diagnostic or prognostic disease specific biomarkers available in the clinic. The primary aim of the present study was to develop a targeted mass spectrometry assay for simultaneous quantification of 30 brain-related proteins in CSF and subsequently to demonstrate assay feasibility in neurological samples derived from multiple sclerosis patients. Our multiplex selected reaction monitoring assay had wide dynamic range (median fold range across peptides = 8.16 × 10³) and high assay reproducibility (median across peptides CV = 4%). Candidate biomarkers were quantified in CSF samples from neurologically healthy individuals (n = 9) and patients diagnosed with clinically isolated syndrome (n = 29) or early multiple sclerosis (n = 15).

Blood Glucose Determination: Effect of Tube Additives

The measurement of fasting plasma glucose may be biased by a time-dependent decrease of glucose in blood tubes, mainly attributable to blood cell metabolism when glycolysis is not rapidly inhibited or blood cells cannot be rapidly separated from plasma. Although glycolysis inhibitors such as sodium fluoride (NaF) in combination with potassium oxalate (KOx) are currently used for overcoming this drawback, their efficacy for stabilizing blood glucose is seemingly limited, and probably lower than that of newer additives such as the citrate buffer. Therefore, we performed a critical analysis of the current scientific literature aimed to generate evidence-based information about the advantages of using citrate buffer in blood tubes compared to the more conventional NaF additive. The results of our systematic overview of the literature show that citrate blood tubes represent a considerable step forward in achieving more accurate and reliable plasma glucose measurements, thereby limiting the risk of underdiagnosing diabetes due to spurious decrease of glucose concentration in uncentrifuged blood specimens, ensuring higher stability of glucose levels over time, while simultaneously producing less hemolysis compared to NaF blood tubes. Therefore, we suggest that the use of this new mixture should be encouraged for achieving a higher degree of accuracy and standardization of plasma glucose measurements.

Short Term Changes of Serum Lipids in Acute Ischemic Stroke

BACKGROUND

Temporal pattern of lipids changes in stroke patients and its prognostic significance has not yet been fully understood. Our aim was to assess the early temporal changes of lipids in acute ischemic stroke patients and its prognostic significance in predicting stroke outcome.

METHODS

Total cholesterol, LDL-cholesterol, HDL-cholesterol and triglycerides were measured at admission, 24 hours, 48 hours, 72 hours, and at discharge. Stroke outcome was assessed by infarct volume, neurological deficit at discharge and 90 days stroke mortality. We have included only patients for whom blood and all clinical data were available at all time points during the follow-up period.

RESULTS

In our stroke cohort (n = 52) there was a mean decrease of HDL-cholesterol from admission to discharge (0.32 mmol/L, 23%), accompanied with an increase in triglyceride concentration of 0.3 mmol/L (8%). LDL-cholesterol and total cholesterol had an initial rise at 24 hours, followed by the subsequent fall at 48 hours, 72 hours, and at discharge. Decreased HDL-cholesterol at 48 hours after stroke onset and at discharge is associated with poor patient functional outcome. Patients with large infarct volume had significantly higher concentrations of total cholesterol and LDL-cholesterol at 24 hours, 48 hours, and at discharge than patients with small and medium infarct volume.

CONCLUSIONS

Early after the onset of acute ischemic stroke there is a marked change in the concentration of serum lipids. Reliable assessment of lipid status cannot be done during the early period after the stroke onset.

The alcohol used for cleansing the venipuncture site does not jeopardize blood and plasma alcohol measurement with head-space gas chromatography and an enzymatic assay

Introduction

This study aimed to establish whether an alcoholic antiseptic, wiped or not before venipuncture, may jeopardize alcohol testing with a commercial enzymatic assay and a reference head-space gas chromatography (GC) technique.

Materials and methods

Venous blood was collected from 23 healthy volunteers, with two sequential procedures. In the first blood collection, 2 mL of alcoholic antiseptic (0.5% chlorhexidine, 70% ethanol) were place on a gauge pad, the venipuncture site of right arm was cleaned but the antiseptic was not let to dry before phlebotomy. In the second blood collection, 2 mL of the same alcoholic antiseptic were placed on another gauge pad, the venipuncture site of left harm was cleaned and the antiseptic was accurately cleansed before phlebotomy. Ethanol was measured with a reference GC technique in whole blood and EDTA plasma, and a commercial enzymatic assay in EDTA plasma.

Results

No subject complained about feeling a particular itchy sensation when the alcohol was not wiped before puncturing the vein. The concentration of alcohol in all EDTA plasma samples was always lower than the limit of detection of the enzymatic assay (i.e., 2.2 mmol/L; 0.1 g/L). Similarly, alcohol concentration was also undetectable using a reference GC technique (i.e., < 0.22 mmol/L; 0.01 g/L) in EDTA plasma and whole blood.

Conclusion

It seems reasonable to conclude that using ethanol-containing antiseptics before venipuncture may not be causes of spurious or false positive results of alcohol measurement at least when ideal venipunctures can be performed.

Critical laboratory values in hemostasis: toward consensus

The term "critical values" can be defined to entail laboratory test results that significantly lie outside the normal (reference) range and necessitate immediate reporting to safeguard patient health, as well as those displaying a highly and clinically significant variation compared to previous data. The identification and effective communication of "highly pathological" values has engaged the minds of many clinicians, health care and laboratory professionals for decades, since these activities are vital to good laboratory practice. This is especially true in hemostasis, where a timely and efficient communication of critical values strongly impacts patient management. Due to the heterogeneity of available data, this paper is hence aimed to analyze the state of the art and provide an expert opinion about the parameters, measurement units and alert limits pertaining to critical values in hemostasis, thus providing a basic document for future consultation that assists laboratory professionals and clinicians alike. KEY MESSAGES Critical values are laboratory test results significantly lying outside the normal (reference) range and necessitating immediate reporting to safeguard patient health. A broad heterogeneity exists about critical values in hemostasis worldwide. We provide here an expert opinion about the parameters, measurement units and alert limits pertaining to critical values in hemostasis.