Laboratory Anomalies in the Basic Metabolic Panel: Core Curriculum 2025.

Laboratory testing plays an integral part in medical decision making. However, laboratory results can sometimes vary significantly, leading to anomalous outcomes that are not consistent with the clinical picture. These anomalies can occur even in the best of laboratories simply because the total testing process includes elements that are not totally under the laboratory's control. For example, variations in patient preparation and sample collection procedures, as can happen at physician offices or patients receiving intravenous fluids, are major contributors to these anomalies. Therefore, physicians must remain aware of the causes of these anomalies so they can consider them when interpreting laboratory results and help implement solutions to mitigate them at their respective institutions. This Core Curriculum examines several instances where an understanding of preanalytical, analytical, and postanalytical variation is essential for detecting anomalies and providing proper patient care.

Faecal immunochemical testing (FIT): sources of result variation based on three years of routine testing of symptomatic patients in English primary care.

Introduction: We aimed to determine the analytical capabilities of a commonly used faecal immunochemical test (FIT) to detect faecal haemoglobin (Hb) in symptomatic people attending primary care in the context of the English NICE DG30 guidance.Materials and Methods: Data obtained from independent verification studies and clinical testing of the HM-JACKarc FIT method in routine primary care practice were analysed to derive performance characteristics.Results: Detection capabilities for the FIT method were 0.5 µg/g (limit of blank), 1.3 µg/g (limit of detection) and 3.0 µg/g (limit of quantitation). Of 33 non-homogenized specimens, 31 (93.9%) analysed in triplicate were consistently categorized relative to 10 µg/g, compared to all 33 (100%) homogenized specimens. Imprecision was higher (median 27.8%, (range 20.5% to 48.6%)) in non-homogenized specimens than in homogenized specimens (10.2%, (7.0 to 13.5%)). Considerable variation was observed in sequential clinical specimens from individual patients but no positive or negative trend in specimen degradation was observed over time (p = 0.26).Discussion: The FIT immunoassay evaluated is capable of detecting faecal Hb at concentrations well below the DG30 threshold of 10 µg/g and is suitable for application in this context. The greatest practical challenge to FIT performance is reproducible sampling, the pre-analytical step associated with most variability. Further research should focus on reducing sampling variability, particularly as post-COVID-19 guidance recommends greater FIT utilization.

Development of blood-based biomarker tests for early detection of colorectal neoplasia: Influence of blood collection timing and handling procedures.

INTRODUCTION: Blood-based, cancer-associated biomarkers are susceptible to a variety of well-known preanalytical factors. The influence of bowel preparation before a diagnostic colonoscopy on biomarker levels is, however, poorly investigated. The present study assessed the influence of bowel preparation on colorectal cancer-associated biomarkers. In addition, the effect of single versus double centrifugation of plasma biomarkers was assessed. METHODS: Blood samples were collected pre- and post-bowel preparation from 125 subjects scheduled for first time diagnostic colonoscopy due to symptoms attributable to CRC. The samples were separated into serum and EDTA plasma, and analyzed by four independent collaborators for: 1) the proteins AFP, CA19-9, CEA, hs-CRP, CyFra21-1, Ferritin, Galectin-3 and TIMP-1, 2) the proteins BAG4, IL6ST, vWF, CD44 and EGFR, 3) the glycoprotein Galectin-3 ligand, and 4) cell-free DNA (cfDNA). Statistical analysis of biomarker data has been performed using mixed modelling, including repeated measures. RESULTS: The biomarkers generally showed negligible variation between pre- and post-bowel preparation except for CyFra21-1, Ferritin, BAG4 and cfDNA. CyFra21-1 levels were systematically reduced with 29% (95% CI 21-36%) by bowel preparation (p ≤ 0.0001). Ferritin was not significantly different between pre- and post-bowel preparation (p = 0.07), however the estimated difference (increase) was 18%. BAG4 was systematically reduced by 12% (95% CI 1-22%, p = 0.04), while cfDNA showed a significant increase of 28% (95% CI 17-39%, p < 0.0001). Double centrifugation compared to single centrifugation showed reduced vWF (ratio 0.86, p ≤ 0.0001) and CD44 (ratio 0.85, p = 0.016), but increased IL6ST levels (ratio 1.18, p = 0.014). CONCLUSIONS: Results of the present study demonstrated systematic, statistically significant differences between pre-bowel and post-bowel preparation levels for three independent blood-based biomarkers (BAG4, CyFra21-1, cfDNA), illustrating the importance of timing of sample collection for biomarker analyses.

How to handle adsorption of cerebrospinal fluid amyloid ß (1-42) in laboratory practice? Identifying problematic handlings and resolving the issue by use of the Aß42/Aß40 ratio.

INTRODUCTION: We aimed to investigate factors defining amyloid ß (1-42) (Aß1-42) adsorption during preanalytical workup of cerebrospinal fluid (CSF). METHODS: CSF was transferred to new tubes ≤4 times. Variables tested were different polypropylene tube brands, volumes, CSF Aß1-42 concentrations, incubation times, pipettes, vortex intensities, and other CSF proteins, including hyperphosphorylated tau and Interleukin 1 Receptor Accessory Protein (IL-1RAcP). An enquiry assessed the number of transfers in current practice. RESULTS: In diagnostic practice, the number of transfers varied between 1 and 3. Every tube transfer resulted in 5% loss of Aß1-42 concentration, even 10% in small volumes. Adsorption was observed after 30 seconds and after contact with the pipette tip. Tube brand, vortexing, or continuous tube movement did not influence adsorption. Adsorption for Aß1-40 was similar, resulting in stable Aß1-42/Aß1-40 ratios over multiple tube transfers. DISCUSSION: We confirmed that adsorption of CSF Aß1-42 during preanalytical processing is an important confounder. However, use of the Aß1-42/Aß1-40 ratio overcomes this effect and can therefore contribute to increased diagnostic accuracy.

Saliva as a diagnostic fluid in sports medicine: potential and limitations / Saliva como fluido diagnóstico para utilização na medicina esportiva: potencialidades e limitações

The use of saliva in the diagnosis of pathologies and/or monitoring of athletes in competitions or trainings is an attractive alternative due to the fact that samples are easily obtained and it is mostly a less invasive method in comparison with venous blood collection. The saliva is a hypotonic fluid in relation to plasma, containing compounds produced in the salivary glands (immunoglobulin A [IgA] and α-amylase) as well as compounds diffused in the plasma (water, electrolytes, proteins, metabolites and hormones). It plays a pivotal role in the protection of oral mucosa against microbes and in food digestion. Its production and composition depend on the sympathetic and parasympathetic nervous system activity, whose antagonistic action may result in different saliva volumes with distinct ionic and protein profiles. The aim of this review was to present a critical analysis of the potential and limitations of saliva as a diagnostic tool in sports medicine. Although there are studies that have deployed it to monitor athletes in training and doping, the standardization of some preanalytical variables are still required, among which the following ones are worth mentioning: the accurate choice of collection system, which allows the easy quantification of volume with adequate sample recovery; well-defined collection schedules in accordance with the circadian variations of the analyte; prevention of sample contamination with blood from oral mucosa lesions. Another key point for its application in sports is the establishment of reference intervals for analytes quantified in the saliva, collected from a population that comprises healthy individual that exercise regularly and systematically, with physical activity progression.

A utilização de saliva como alternativa para o diagnóstico de patologias e/ou monitoramento de atletas em competições ou treinos é muito atrativa devido à facilidade de obtenção da amostra e, principalmente, pela natureza menos invasiva que a coleta de sangue venoso. A saliva é um fluído hipotônico em relação ao plasma; contém compostos produzidos localmente nas glândulas salivares (imunoglobulina A [IgA] e α-amilase), além de compostos difundidos do plasma (água, eletrólitos, proteínas, metabólitos e hormônios). A saliva desempenha funções importantes na proteção da mucosa oral contra microrganismos e na digestão dos alimentos. Sua produção e sua composição são dependentes da atividade do sistema nervoso autônomo simpático e parassimpático, cuja ação antagônica pode resultar em diferentes volumes de saliva com perfis proteico e iônico distintos. O objetivo da presente revisão é apresentar uma análise crítica das potencialidades e limitações da utilização da saliva como ferramenta diagnóstica para a medicina esportiva. Embora existam estudos que a utilizam para o monitoramento de atletas em situações de exercício e doping, ainda é necessário padronizar algumas variáveis pré-analíticas, como a escolha correta do melhor sistema de coleta, que permite quantificar facilmente o volume, com boa recuperação de amostra; os horários de coleta bem definidos, de acordo com as possíveis variações circadianas do analito; e a contaminação da saliva com sangue proveniente de lesões da mucosa oral, que tem de ser evitada. Outro ponto fundamental para aplicação no esporte é o estabelecimento de valores de referência para analitos quantificados na saliva, obtidos de uma população composta de sujeitos saudáveis e exercitados de forma constante e sistematizada, com progressão de cargas de esforço.