Laboratory Medicine Research Articles

The hierarchy of needs for laboratory medicine requires a foundational care delivery model

Under the collective weight of growing test volume, staffing constraints, and Medicare reimbursements cuts, an enhancement-based, alternative payment structure focused on rewarding the laboratory's care delivery efforts via benchmarking is appealing. However, achieving a value-based payment model requires the development of an inclusive laboratory care delivery model (LCDM) framework. Today, a holistic, practical LCDM framework for laboratory medicine does not exist. However, such creation is essential for establishing unifying tenants of practice for value-tracing by which standardized key performance and population health indicators can be derived. LAB-CARES is the first step in formulating an LCDM with the primary objective of defining and streamlining the processes and strategies necessary to deliver and articulate the value of diagnostic excellence across the healthcare system. The goal of LAB-CARES is to maximize efficiencies, enhance quality, disseminate clinical expertise, increase patient safety, and promote integrative practice. LAB-CARES is designed to improve an individual patient's quality of life (longitudinal laboratory results – beyond one test) and their surrounding communities (e.g., through surveillance and prevention – beyond one patient). Further professional conversation and efforts are paramount to integrate LAB-CARES as a formalized structure within the healthcare landscape.

Machine Learning for Patient-Based Real-Time Quality Control (PBRTQC), Analytical and Preanalytical Error Detection in Clinical Laboratory.

The rapidly evolving field of machine learning (ML), along with artificial intelligence in a broad sense, is revolutionising many areas of healthcare, including laboratory medicine. The amalgamation of the fields of ML and patient-based real-time quality control (PBRTQC) processes could improve the traditional PBRTQC and error detection algorithms in the laboratory. This narrative review discusses published studies on using ML for the detection of systematic errors, non-systematic errors, and combinations of different types of errors in clinical laboratories. The studies discussed used ML for detecting bias, the requirement for re-calibration, samples contaminated with intravenous fluid or EDTA, delayed sample analysis, wrong-blood-in-tube errors, interference or a combination of different types of errors, by comparing the performance of ML models with human validators or traditional PBRTQC algorithms. Advantages, limitations, the creation of standardised ML models, ethical and regulatory aspects and potential future developments have also been discussed in brief.

Health disparities among incarcerated populations: a crucial laboratory and pathology review.

The United States notoriously has one of the highest rates of incarceration in the world, yet scant attention to the health care needs of those incarcerated exists within laboratory medicine and pathology training and education. This article explores health disparities among incarcerated and released individuals regarding diagnostic laboratory testing and pathology services. A literature search was conducted for articles published between 2002 and 2023 using keywords including "healthcare," "incarcerated," "laboratory services," "pathology services," and "health insurance for prisoners." Central themes were extracted and discussed to reveal the realities of health care during and after release from incarceration. Excluded from the analysis were articles about the immediate or extended family of incarcerated persons. Incarcerated individuals have an increased risk for the development and exacerbation of communicable and noncommunicable diseases and mental health disorders, which results in exceedingly high morbidity and mortality rates. Policy changes are needed to mitigate disparities and improve health outcomes for incarcerated and released persons. Central to these disparities is decreased access to laboratory and pathology services, impeded by inadequate health care funding for these carceral institutions. Providing additional funding to the carceral system's health care budget is necessary to improve access to pathology and laboratory services.

Evaluation of AI-Driven LabTest Checker for Diagnostic Accuracy and Safety: Prospective Cohort Study.

In recent years, the implementation of artificial intelligence (AI) in health care is progressively transforming medical fields, with the use of clinical decision support systems (CDSSs) as a notable application. Laboratory tests are vital for accurate diagnoses, but their increasing reliance presents challenges. The need for effective strategies for managing laboratory test interpretation is evident from the millions of monthly searches on test results' significance. As the potential role of CDSSs in laboratory diagnostics gains significance, however, more research is needed to explore this area. The primary objective of our study was to assess the accuracy and safety of LabTest Checker (LTC), a CDSS designed to support medical diagnoses by analyzing both laboratory test results and patients' medical histories. This cohort study embraced a prospective data collection approach. A total of 101 patients aged ≥18 years, in stable condition, and requiring comprehensive diagnosis were enrolled. A panel of blood laboratory tests was conducted for each participant. Participants used LTC for test result interpretation. The accuracy and safety of the tool were assessed by comparing AI-generated suggestions to experienced doctor (consultant) recommendations, which are considered the gold standard. The system achieved a 74.3% accuracy and 100% sensitivity for emergency safety and 92.3% sensitivity for urgent cases. It potentially reduced unnecessary medical visits by 41.6% (42/101) and achieved an 82.9% accuracy in identifying underlying pathologies. This study underscores the transformative potential of AI-based CDSSs in laboratory diagnostics, contributing to enhanced patient care, efficient health care systems, and improved medical outcomes. LTC's performance evaluation highlights the advancements in AI's role in laboratory medicine.

External quality assurance experience with Royal College of Pathologists of Australasia Program at an academic hospital in South Africa.

Laboratories use their performance in external quality assurance (EQA) to establish quality planning strategies and to assess whether testing processes require improvement. The EQA performance of the hematology and coagulation test parameters on the Royal College of Pathologists of Australasia EQA program was evaluated over a 4-year cycle at an academic hospital in Johannesburg, South Africa. The test performance was determined from analytical quality specification (APS) and/or z-scores. Bias and imprecision were used to calculate sigma (σ) metric scores. Specifications from European Federation of Laboratory Medicine and/or biological variation were applied. The laboratory achieved a mean testing score of 98.7±4.0%. There were 103 (10.7%) unacceptable results. On investigation, root causes included: presurvey issues (83%), transcription errors (9%), random errors (6%), and test performance errors (3%). All test parameters evaluated achieved an acceptable median APS during the study period. The mean z-scores, however, were >2 and unacceptable for mean cell hemoglobin concentration and hematocrit. On investigation, this was attributed to significant delay in transport and storage of full blood count samples. White cell count and d-dimer achieved a σ ≥ 6. EQA participation assisted the laboratory in maintaining a quality system. Close monitoring is necessary for international laboratories to avoid sample delays that can affect result quality.

Application of EXODUS system combined with allosteric DNA nanoswitches in the detection of miR-107 among plasma exosomes of Parkinson's disease patients

This study aimed to achieve rapid detection of Parkinson's disease (PD) plasma exosome miR-107. A case-control design was used to collect ten Parkinson's disease and ten healthy control plasma samples from the Department of Laboratory Medicine, Tongji Hospital, Tongji Medical College of Huazhong University of Science and Technology from December 2023 to January 2024. Exosome detection via the ultrafast-isolation system (EXODUS) was used to isolate plasma exosomes. The nanoparticle tracking analysis technology and electron microscopy were used to identify exosome particle size and morphology. The Qiagen miRNeasy Micro Kit was used to extract RNA. The microRNA-activated conditional looping of engineered switches (miRacles) was used to detect miR-107, and the relative expression was analyzed by agarose gel electrophoresis. Thermo Fisher RevertAid RT Reverse Transcription Kit was used to perform reverse transcription of RNA, and real-time PCR was used to detect miR-107. The independent samples t-test was used for comparison between groups. EXODUS system completed the isolation of exosomes from 500 μl plasma within 1.5 hours. The exosome concentration (mean±SD) was (4.82±2.02)×1010 particles/ml in the control group and (5.08±2.34)×1010 particles/ml in the PD group. There was no significant difference in exosome concentration between PD patients and healthy controls (t=-0.168, P=0.872). The morphology of exosomes was confirmed by electron microscopy. The miRacles nanoswitch could detect fM-level miR-107 and also effectively distinguish miR-107 from its family members, including miR-15a and miR-16. Agarose gel electrophoresis showed that the mean±SD of relative grey value content was 1.00±0.26 in the control group and 1.86±0.21 in the PD group. The miR-107 in the PD group was significantly higher than that in the control (t=-8.143, P<0.001), which was consistent with the result of real-time PCR. EXODUS combined with miRacles could achieve rapid, non-enzymatic and cheap detection of plasma exosomal miR-107 in PD patients.

Direct, age- and gender-specific reference intervals: applying a modified M-estimator of the Yeo-Johnson transformation to clinical real-world data

Abstract Objectives Reference intervals for the general clinical practice are expected to cover non-pathological values, but also reflect the underlying biological variation present in age- and gender-specific patient populations. Reference intervals can be inferred from routine patient data measured in high capacity using parametric approaches. Stratified reference distributions are obtained which may be transformed to normality via e.g. a Yeo-Johnson transformation. The estimation of the optimal transformation parameter for Yeo-Johnson through maximum likelihood can be highly influenced by the presence of outlying observations, resulting in biased reference interval estimates. Methods To reduce the influence of outlying observations on parametric reference interval estimation, a reweighted M-estimator approach for the Yeo-Johnson (YJ) transformation was utilised to achieve central normality in stratified reference populations for a variety of laboratory test results. The reweighted M-estimator for the YJ transformation offers a robust parametric approach to infer relevant reference intervals. Results The proposed method showcases robustness up to 15 % of outliers present in routine patient data, highlighting the applicability of the reweighted M-estimator in laboratory medicine. Furthermore, reference intervals are personalised based on the patients’ age and gender for a variety of analytes from routine patient data collected in a tertiary hospital, robustly reducing the dimensionality of the data for more data-driven approaches. Conclusions The method shows the advantages for estimating reference intervals directly and parametrically from routine patient data in order to provide expected reference ranges. This approach to locally inferred reference intervals allows a more nuanced comparison of patients’ test results.

German Congress of Laboratory Medicine: 19th Annual Congress of the DGKL and 6th Symposium of the Biomedical Analytics of the DVTA e. V. together with the 6th German POCT-Symposium

German Congress of Laboratory Medicine: 19th Annual Congress of the DGKL and 6th Symposium of the Biomedical Analytics of the DVTA e. V. together with the 6th German POCT-Symposium

Enhancing precision through AI-enhanced method verification validating iron determination on the Alinity ci® Analyzer: Experience of the central laboratory of Mohammed VI University Hospital of Oujda

This study meticulously assessed the analytical performance of iron determination on the Alinity ci® analyzer, employing advanced AI-powered method verification techniques. Conducted at Mohammed VI University Hospital's central laboratory in Oujda, Morocco, the validation process strictly adhered to the rigorous guidelines outlined in the French accreditation committee's (COFRAC) Accreditation Technical Guide (GTA) 04. Through comprehensive assessments of repeatability and reproducibility, we definitively confirmed the assay's precision and reliability. Our evaluation yielded highly satisfactory results, consistently exceeding the established criteria set forth by both the instrument manufacturer and esteemed professional organizations like SFBC and RICOS. This unequivocally validates the laboratory's capability to deliver accurate and reproducible iron concentration measurements, crucial for enhanced clinical diagnostics and, ultimately, well-informed patient care decisions. This study underscores the importance of stringent validation processes in ensuring the reliability of diagnostic assays, thereby bolstering confidence in laboratory medicine practices and patient outcomes.

Advancing value-based laboratory medicine.

Following the COVID-19 pandemic, the concepts of value-based medicine (VBM) and value-based laboratory medicine (VBLM) are receiving increasing interest to improve the quality, sustainability and safety of healthcare. Laboratory medicine is well positioned to support the transition to value-based healthcare as it helps to improve clinical outcomes and healthcare sustainability by reducing the time to diagnosis, improving diagnostic accuracy, providing effective guidance for tailored therapies and monitoring, and supporting screening and wellness care. However, the perception of the value of laboratory medicine is still limited, to the extent that it has been defined a "profession without a face", often lacking visibility to patients and the public. In addition, in recent decades, clinical laboratories have sought to improve the ration between outcomes and costs by increasing efficiency and reducing the cost per test rather than improving clinical outcomes. The aim of this paper is to propose a 10-point manifesto for implementing value-based laboratory medicine in clinical practice.

Bilirubin measurements in neonates: uniform neonatal treatment can only be achieved by improved standardization.

Measurement of total bilirubin (TBil) concentration in serum is the gold standard approach for diagnosing neonatal unconjugated hyperbilirubinemia. It is of utmost importance that the measured TBil concentration is sufficiently accurate to prevent under treatment, unnecessary escalation of care, or overtreatment. However, it is widely recognized that TBil measurements urgently require improvement in neonatal clinical chemistry. External quality assessment (EQA) programs for TBil assess for differences between laboratories and provide supporting evidence of significant differences between various methods, manufacturers and measurement platforms. At the same time, many countries have adopted or only slightly adapted the neonatal hyperbilirubinemia management guidelines from the USA or UK, often without addressing differences in the methodology of TBil measurements. In this report, we provide an overview of the components of bilirubin that are measured by laboratory platforms, the availability of current reference measurement procedures and reference materials, and therole of EQA surveys in this context. Furthermore, the current status of agreement in neonatal bilirubin against clinical decision thresholds is reviewed. We advocate for enhancements in accuracy and comparability of neonatal TBil measurements, propose a path forward to accomplish this, and reflect on the position of the International Federation for Clinical Chemistry and Laboratory Medicine (IFCC) Working Group Neonatal Bilirubin (WG-NB) in this matter.

Considerations for applying emerging technologies in paediatric laboratory medicine.

Emerging technology in laboratory medicine can be defined as an analytical method (including biomarkers) or device (software, applications, and algorithms) that by its stage of development, translation into broad routine clinical practice, or geographical adoption and implementation has the potential to add value to clinical diagnostics. Paediatric laboratory medicine itself may be considered an emerging area of specialisation that is established relatively recently following increased appreciation and understanding of the unique physiology and healthcare needs of the children. Through four clinical (neonatal hypoglycaemia, neonatal hyperbilirubinaemia, sickle cell disorder, congenital adrenal hyperplasia) and six technological (microassays, noninvasive testing, alternative matrices, next generation sequencing, exosome analysis, machine learning) illustrations, key takeaways of application of emerging technology for each area are summarised. Additionally, nine key considerations when applying emerging technology in paediatric laboratory medicine setting are discussed.

HTA model for laboratory medicine technologies: overview of approaches adopted in some international agencies.

The Health Technology Assessment (HTA) Working Group of the Emerging Technology Division of International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) aims to develop a methodological approach for producing structured HTA information for laboratory medicine technologies. This approach seeks to support decision-making processes at the country, regional, and/or hospital levels regarding the introduction of specific technologies. The focus of this model will primarily be ondefining assessment elements within the domains of 'organizational aspects' and 'costs and economic evaluations', potentially differentiated by the type of diagnostic technology (e.g., genetic tests, molecular tests). To achieve this project's goal, a literature review and examination ofwebsites of international HTA agencies have been conducted. The research aims to identify multidisciplinary methodological approaches used to assess laboratory diagnostic technologies and to pinpoint the domains and assessment elements utilized. Wefound 7 methodological articles describing methodological approaches adopted toassess laboratory diagnostic technologies. Among the HTA organizations considered, 23 reports were found, of which 7 were produced by the European Network of HTA (EUnetHTA), 4 by the National Institute for Health and Care Excellence Diagnostic Assessment Program (NICE DAP), and 12 by other HTA agencies. The EUnetHTA reports wererapid collaborative assessments covering various domains, while the NICE DAP reports focused on diagnostic guidances, including descriptions of technologies, clinical need and practice, diagnostic tests, accuracy, effectiveness, and cost-effectiveness. Finally, a survey targeting laboratory professionals will be conducted to introduce assessment elements, differentiated by the type of diagnostic technology, primarily for organizational and economic domains.

A candidate reference measurement procedure for quantification of glycocholic acid in human serum based on isotope dilution liquid chromatography-tandem mass spectrometry

Accurate measurement of serum glycocholic acid (GCA) is crucial for evaluating the activity of chronic hepatitis. Moreover, GCA is a novel identified biomarker for hepatocellular carcinoma. Although some laboratories have used the liquid chromatography-tandem mass spectrometry (LC–MS/MS) method to measure GCA in recent years, the problem of potential interference of GCA analogues has not been solved well yet. Neither reference measurement procedures nor reference materials for GCA have been listed in the Joint Committee for Traceability in Laboratory Medicine (JCTLM) database. For standardization of GCA, it is urgent to establish a candidate measurement procedure for GCA. In this study, a candidate reference measurement procedure for the quantification of GCA in human serum based on isotope dilution liquid chromatography-tandem mass spectrometry (ID-LC–MS/MS) by a two-step sample pretreatment of protein precipitation and MAX solid-phase extraction was developed and validated. GCA can be completely separated from its structural analogues with gradient elution in 9 min compared with short time gradients published in previous literature by Huang’s group. Method validation indicated perfect quantitation precision with intra-day and inter-day values that were ≤1.30% and ≤1.80%, respectively. The method showed excellent linearity with high regression coefficients (R2 > 0.999) over a range of 0.92 ng/g–38.38 μg/g and perfect recoveries at three spiked levels (99.87–100.43%). No interference, matrix effect, and carryover were observed. Moreover, the cRMP was successfully applied to measure GCA in serum samples and compared with two immunoassays in a clinical laboratory. As a candidate reference method, this method can promote a GCA standardization program.Graphical

Analytical performance specifications for trace elements in biological fluids derived from six countries federated external quality assessment schemes over 10 years.

This article defines analytical performance specifications (APS) for evaluating laboratory proficiency through an external quality assessment scheme. Standard deviations for proficiency assessment were derived from Thompson's characteristic function applied to robust data calculated from participants' submissions in the Occupational and Environmental Laboratory Medicine (OELM) external quality assurance scheme for trace elements in serum, whole blood and urine. Characteristic function was based on two parameters: (1) β- the average coefficient of variation (CV) at high sample concentrations; (2) α- the average standard deviation (SD) at low sample concentrations. APSs weredefined as 1.65 standard deviations calculated by Thompson's approach. Comparison between OELM robust data and characteristic function were used to validate the model. Application of the characteristic function allowed calculated APS for 18 elements across three matrices. Some limitations were noted, particularly for elements (1) with no sample concentrations near analytical technique limit of detection; (2) exhibiting high robust CV at high concentration; (3) exhibiting high analytical variability such as whole blood Tl and urine Pb; (4) with an unbalanced number of robust SD above and under the characteristic function such as whole blood Mn and serum Al and Zn. The characteristic function was a useful means of deriving APS for trace elements in biological fluids where biological variation data or outcome studies were not available. However, OELM external quality assurance scheme data suggests that the characteristic functions are not appropriate for all elements.

EFLM Task Force Preparation of Labs for Emergencies (TF-PLE) recommendations for reinforcing cyber-security and managing cyber-attacks in medical laboratories.

The healthcare systems are a prime target for cyber-attacks due to the sensitive nature of the information combined with the essential need for continuity of care. Medical laboratories are particularly vulnerable to cyber-attacks for a number of reasons, including the high level of information technology (IT), computerization and digitization. Based on reliable and widespread evidence that medical laboratories may be inadequately prepared for cyber-terrorism, a panel of experts of the Task Force Preparation of Labs for Emergencies (TF-PLE) of the European Federation of Clinical Chemistry and Laboratory Medicine (EFLM) has recognized the need to provide some general guidance that could help medical laboratories to be less vulnerable and better prepared for the dramatic circumstance of a disruptive cyber-attack, issuing a number of consensus recommendations, which are summarized and described in this opinion paper.

ChatGPT vs Medical Professional: Analyzing Responses to Laboratory Medicine Questions on Social Media.

The integration of ChatGPT, a large language model (LLM) developed by OpenAI, into healthcare has sparked significant interest due to its potential to enhance patient care and medical education. With the increasing trend of patients accessing laboratory results online, there is a pressing need to evaluate the effectiveness of ChatGPT in providing accurate laboratory medicine information. Our study evaluates ChatGPT's effectiveness in addressing patient questions in this area, comparing its performance with that of medical professionals on social media. This study sourced patient questions and medical professional responses from Reddit and Quora, comparing them with responses generated by ChatGPT versions 3.5 and 4.0. Experienced laboratory medicine professionals evaluated the responses for quality and preference. Evaluation results were further analyzed using R software. The study analyzed 49 questions, with evaluators reviewing responses from both medical professionals and ChatGPT. ChatGPT's responses were preferred by 75.9% of evaluators and generally received higher ratings for quality. They were noted for their comprehensive and accurate information, whereas responses from medical professionals were valued for their conciseness. The interrater agreement was fair, indicating some subjectivity but a consistent preference for ChatGPT's detailed responses. ChatGPT demonstrates potential as an effective tool for addressing queries in laboratory medicine, often surpassing medical professionals in response quality. These results support the need for further research to confirm ChatGPT's utility and explore its integration into healthcare settings.

Antibacterial activity of Balinese Traditional Herbs Elephantopus Scaber Linn and Curcuma aeruginosa Roxb against Burkholderia pseudomallei, Staphylococcus aureus, and Salmonella typhimurium

Background: Herbal medicinal plants are considered one of the sources for new types of antibiotics due to their secondary metabolite that may have antibacterial effects. Tapak Liman (Elephantopus scaber linn) and Temu Ireng (Curcuma aeruginosa roxb) are two medicinal plants that have potential as antibacterial agents due to their secondary metabolite contents. This study aimed to investigate the secondary metabolite contents of tapak liman and temu ireng grown locally in Bali and their antibacterial activity against Burkholderia pseudomallei, Staphylococcus aureus, and Salmonella typhimurium. Methods: This post-test experimental research was conducted from June to December 2021 at the Universitas Warmadewa Faculty of Medicine and Health Sciences Research Laboratory. Tapak liman leaves and temu ireng rhizomes, sourced from a local garden in Denpasar, Bali, were used. Ethanolic extracts of these plants were tested for secondary metabolites and their antibacterial activity against Staphylococcus aureus, Salmonella typhimurium, and Burkholderia pseudomallei. Results: A phytochemical analysis of tapak liman from Denpasar shows that it contains alkaloids and phenols, while temuireng contains flavonoids, tannins, and phenols. Antibacterial tests revealed that both plants have a weak effect against gram-positive Staphylococcus aureus but negligible effect against gram-negative Burkholderia pseudomallei and Salmonella typhimurium. Conclusion: Both tapak liman and temu ireng ethanolic extract have weak antibacterial properties against gram-positive Staphylococcus aureus and negligible/no antibacterial properties against gram-negative Burkholderia pseudomallei and Salmonella typhimurium.

The surveys on quality indicators for the total testing process in clinical laboratories of Fujian Province in China from 2018 to 2023.

This study investigates the application of 15 Quality Indicators (QIs) in clinical laboratories in Fujian Province, China, from 2018 to 2023. It identifies the main causes of laboratory errors and explores issues in the application of QIs, providing a reference for establishing provincial state-of-the-art and operational quality specifications (QSs). All clinical laboratories in Fujian Province were organized to submit general information and original QIs data through the online External Quality Assessment (EQA) system of the National Clinical Laboratory Center (NCCL) for a survey of 15 QIs. Data from 2018 to 2023 were downloaded for statistical analysis, and the current QSs for the 15 QIs in Fujian Province were compared and analyzed with those published by the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) Working Group on Laboratory Errors and Patient Safety (WG-LEPS). QIs data from 542 clinical laboratories were collected. The survey on data sources showed that the number of laboratories recording QIs data using Laboratory Information Systems (LIS) increased annually, but the growth was modest and the proportion was less than 50 %. Among the laboratories using LIS to record QIs data, 133 continuously participated in this survey for six years, reporting different QIs. Over the six years, all reported QIs showed significant improvement or at least remained stable. The best median Sigma (σ) metrics were for the percentage of critical values notification and timely critical values notification, reaching 6σ, followed by the percentage of incorrect laboratory reports, with σ metrics ranging from 4.9σ to 5.1σ. In contrast, the percentage of tests covered by internal quality control (IQC) (1.5σ-1.7σ) and inter-laboratory comparison (0.1σ) remained consistently low. Compared to the QSs published by IFCC WG-LEPS, the QSs for the 15 QIs in Fujian Province in 2023 were stricter or roughly equivalent, except for the percentage of incorrect laboratory reports (Fujian Province: 0-0.221, IFCC WG-LEPS: 0-0.03). 1. The application of QIs has significantly improved the quality of testing in clinical laboratories in Fujian Province, but the percentage of tests covered by IQC and inter-laboratory comparison remain low; 2. Effective application of QIs requires the establishment of comprehensive LIS, unified calculation standards, and other supporting measures.

Interference by vitamin B12-macrocomplexes: towards an effective detection and correct interpretation of hypo- and hypervitaminemia

Abstract Objectives The presence of macro-B12 is a cause of factual hypervitaminemia B12. Precipitation with polyethylene glycol (PEG) is a simple method of removing high-molecular-weight biomolecules. However, “free” molecule may co-precipitate. This fact imposes the need to establish new reference values for the post-precipitation result. The main aims of the study were to (Baeza I, Corchón A, Pérez JM, Remacha AF, Rocha H, Rodríguez-Portugal E, et al. Basic Aspects of vitamin B12. In: Communication Committee of the Spanish Society of Laboratory Medicine (SEQCML). Clinical significance of vitamin B12 deficiency. Beyond megaloblastic anemia; 2022. ISBN: 978-84-89975-60-6): establish post-PEG reference intervals (RIs) for total vitamin B12 (Iqtidar N, Chaudary MN. Misdiagnosed vitamin B12 deficiency a challenge to be confronted by use of modern screening markers. J Pak Med Assoc 2012;62:1223–9); compare the two bibliographic criteria for defining the presence of macro-B12 (Green R. Vitamin B12 deficiency from the perspective of a practicing hematologist. Blood 2017;129:2603–11); evaluate the joint usefulness of percentage post-PEG vitamin B12 recovery and post-PEG RIs to inform the real vitamin B12 status; and (Carmel R. Diagnosis and management of clinical and subclinical cobalamin deficiencies: why controversies persist in the age of sensitive metabolic testing. Biochimie 2013;95:1047–55), propose interpretative comments for ease of interpretation. Methods Prospective study in which 488 serum samples from “healthy” individuals were included and analyzed to determine recovery and RIs following PEG precipitation. Subsequently, a retrospective analysis was carried out in order to evaluate the joint usefulness of both definitions for a suspicion of macro-B12. A total of 297 cases were included. Results Recovery and post-PEG RIs determined on an Alinity i platform ranged from 60 to 107 % and from 118 to 506 pmol/L, respectively. McNemar’s test revealed statistically significant differences between both criteria for estimating interference. However, both methodologies showed good agreement. In 27 cases, the presence of macro-B12 coexisted with true hypervitaminemia B12. No case of coexistence of macro-B12 with vitamin B12 deficiency was detected in our series. Conclusions Laboratory reports should include total vitamin B12 concentration, recovery and post-PEG vitamin B12 concentration with their adjusted RIs to better assess the body vitamin status.