Preanalytical and analytical factors affecting laboratory results

Circulating myostatin as a biomarker of muscle mass and strength in individuals with cancer or obesity

BACKGROUND & AIMS

Our study aims to determine whether myostatin (MSTN) is associated with muscle mass and strength in individuals with cancer or obesity, as well as with cancer cachexia (CC) or sarcopenic obesity (SO).

METHODS

The ACTICA study included individuals with CC (n = 70) or without CC (NC, n = 73). The MYDIASECRET study included individuals with obesity evaluated before (T0) and 3 months (T3) after bariatric surgery (n = 62). Body composition was assessed using bioelectrical impedance analysis (BIA). Skeletal muscle mass (SMM) and appendicular SMM (ASMM) were calculated from Janssen's and Sergi's equations, respectively, and expressed as indexes (SMMI and ASMMI). Handgrip strength (HGS) was assessed using a Jamar hand-held dynamometer. MSTN plasma levels were measured using ELISA. Spearman's coefficient was used to correlate MSTN with muscle mass and strength. Receiver operating characteristic (ROC) curve analysis was performed to identify an optimal MSTN cutoff level for the prediction of CC or SO.

RESULTS

In the ACTICA study, muscle mass and strength were lower in CC individuals than in NC individuals (SMMI: 8.0 kg/m2vs 9.0 kg/m2, p = 0.004; ASMMI: 6.2 kg/m2vs 7.2 kg/m2, p < 0.001; HGS: 28 kg vs 38 kg, p < 0.001). MSTN was also lower in CC individuals than in NC individuals (1434 pg/mL vs 2149 pg/mL, p < 0.001). Muscle mass and strength were positively correlated with MSTN (SMMI: R = 0.500, p < 0.001; ASMMI: R = 0.479, p < 0.001; HGS: R = 0.495, p < 0.001). ROC curve analysis showed a MSTN cutoff level of 1548 pg/mL (AUC 0.684, sensitivity 57%, specificity 75%, p < 0.001) for the prediction of CC. In the MYDIASECRET study, muscle mass and strength were reduced at T3 (SMMI: -8%, p < 0.001; ASMMI: -12%, p < 0.001; HGS: -6%, p = 0.005). MSTN was also reduced at T3 (1773 pg/mL vs 2582 pg/mL, p < 0.001). Muscle mass and strength were positively correlated with MSTN at T0 and T3 (SMMI-T0: R = 0.388, p = 0.002; SMMI-T3: R = 0.435, p < 0.001; HGS-T0: R = 0.337, p = 0.007; HGS-T3: R = 0.313, p = 0.013). ROC curve analysis showed a MSTN cutoff level of 4225 pg/mL (AUC 0.835, sensitivity 98%, specificity 100%, p = 0.014) for the prediction of SO at T3.

CONCLUSIONS

MSTN is positively correlated with muscle mass and strength in individuals with cancer or obesity, suggesting its potential use as a biomarker of muscle mass and strength. The ROC curve analysis suggests the potential use of MSTN as a screening tool for CC and SO.

Biological testing during acute psychological stress: A hindrance or an opportunity?

All humans deal with acute psychological stress periodically. Some individuals are affected by needle phobia in which a heightened sense of arousal is precipitated by venepuncture. Acute psychological stress invokes a range of physiological changes including activation of the sympathetic-adrenal-medullary and hypothalamic-pituitary-adrenal axes. In this review article, we first examine the human response to acute stress. We then provide an overview of how psychological stress in a subject is likely to be a source of pre-analytical variability for certain measurands, and the major biochemical markers that have been studied in research aiming to quantify stress. As such, we highlight how stress can be a hindrance to the accurate interpretation of certain laboratory results (particularly cortisol, prolactin, metanephrines and growth hormone), and point out the role that biochemical analysis might play in future studies looking at the effects of stress on human behaviour.

Comparison of Hematological and Biochemical Results Derived from Arterial and Venous Blood Samples in Post-Anesthetic Dogs

Simple Summary

In contrast to humans, general anesthesia is required for both surgical procedures and diagnostic imaging like magnetic resonance imaging (MRI) and computed tomography (CT) in small animals. Because the post-anesthetic period is a particularly high risk time for death, serial monitoring of biochemical and hematological parameters could be required. Blood samples could be collected from an indwelling arterial catheter to avoid stress caused by venipuncture, but studies using arterial blood for hematological and biochemical testing have been limited. The aim of this study is to compare hematological and biochemical results derived from venous and arterial blood samples, and to evaluate their clinical interchangeability in post-anesthetic dogs. We found statistically significant but clinically irrelevant differences in hemoglobin, glucose, creatinine, and calcium levels, and results from venous and arterial blood samples are not clinically interchangeable for gamma-glutamyl transpeptidase and potassium levels.

Abstract

Collecting blood from an indwelling arterial catheter may reduce stress from repeated venipuncture in patients requiring serial monitoring, but the use of arterial blood for hematological and biochemical testing remains understudied. Here, we compared hematological and biochemical results of arterial and venous blood and evaluated their clinical interchangeability. Blood samples from dogs who had recovered from anesthesia, collected by both arterial catheterization and venipuncture, were analyzed. To assess clinical acceptance between paired samples, the limit of agreement between the values derived from the arterial and venous blood samples was compared with the allowable total error (TEa) recommended for each parameter. We found no significant differences between the arterial and venous sample results for red/white blood cell and platelet counts and hematocrit, blood urea nitrogen, phosphate, total protein, albumin, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, gamma-glutamyl transpeptidase, total bilirubin, sodium, potassium, and chloride levels, whereas hemoglobin, glucose, creatinine, and calcium levels differed significantly (p < 0.05). Moreover, only gamma-glutamyl transpeptidase and potassium exceeded the recommended TEa. Hematological and biochemical results derived from venous and arterial blood samples are clinically interchangeable in post-anesthetic dogs, with the exception of gamma-glutamyl transpeptidase and potassium; thus, these values should be used with caution.

Influence of fasting and sample collection time on 38 biochemical markers in healthy children: a CALIPER substudy

OBJECTIVES

Fasting samples can be difficult to obtain in the pediatric setting, particularly in neonates. As part of the Canadian Laboratory Initiative on Pediatric Reference Intervals (CALIPER), we aimed to determine if there are differences in serum concentrations of pediatric biochemical markers measured at fasting, postprandial, and random time points throughout the day.

DESIGN AND METHODS

Blood was drawn from 27 healthy children and adolescents (aged 4-18) with informed consent at 4 time points: after overnight fast, mid-morning after breakfast, within 2h after lunch, and late afternoon. The effect of fasting on 38 chemistries was evaluated by paired, two-tailed student'st-tests. Analysis of the effect of time of day was done using paired, repeated-measures ANOVA.

RESULTS

Fasting significantly affected 22 analytes, with HDL cholesterol being the most highly affected. Values tended to decrease postprandially, except for five analytes, including triglycerides, which increased. By ANOVA, 28 chemistries significantly differed across times of day tested.

CONCLUSIONS

Fasting is necessary for analysis of certain chemistries in pediatric subjects. Pediatricians should consider diurnal factors when ordering non-fasting tests and interpreting test results.

Collection of biological samples in forensic toxicology

Forensic toxicology is the study and practice of the application of toxicology to the purposes of the law. The relevance of any finding is determined, in the first instance, by the nature and integrity of the specimen(s) submitted for analysis. This means that there are several specific challenges to select and collect specimens for ante-mortem and post-mortem toxicology investigation. Post-mortem specimens may be numerous and can endow some special difficulties compared to clinical specimens, namely those resulting from autolytic and putrefactive changes. Storage stability is also an important issue to be considered during the pre-analytic phase, since its consideration should facilitate the assessment of sample quality and the analytical result obtained from that sample. The knowledge on degradation mechanisms and methods to increase storage stability may enable the forensic toxicologist to circumvent possible difficulties. Therefore, advantages and limitations of specimen preservation procedures are thoroughfully discussed in this review. Presently, harmonized protocols for sampling in suspected intoxications would have obvious utility. In the present article an overview is given on sampling procedures for routinely collected specimens as well as on alternative specimens that may provide additional information on the route and timing of exposure to a specific xenobiotic. Last, but not least, a discussion on possible bias that can influence the interpretation of toxicological results is provided. This comprehensive review article is intented as a significant help for forensic toxicologists to accomplish their frequently overwhelming mission.

Implementation of quality control performance criteria and approved guidelines for upgrading of clinical chemistry laboratory procedures in Alexandria University hospitals

The aim of the present work was to assess the quality of work in Clinical Pathology Department, Alexandria Main University Hospital, Egypt; as regards the pre-analytical and analytical phases of testing; for later accreditation. This evaluation was performed using inspection sheets that were designed according to the CAP 2006 recommendations. All checklist questions that could not be answered "yes" were considered deficiencies and had to be corrected before being accredited. The questions were classified into ten groups; each group contained a number of questions concerning one of the pre-analytical and analytical assessment activities. We ranked our results into 4 categories according to the degree of fulfillment. The total number of questions that were answered "no" at the start and the end of the study accounted for 64/101 (63.4%) and 34/101 (33.7%) questions respectively. Most of the deficiencies were detected in the pre-analytical phase of the testing process; the first two checklists were used for the evaluation of this phase. At the start of the study, the degree of requirements fulfillment in checklist I and II were 0% and 21.1% respectively. By the end of the study the degree of fulfillment became, 85.7% and 63.2% respectively. Average number of sample rejection due to different causes was evaluated before and after implementing CAP recommendations; these causes include haemolysis, clotted serum, quantity not sufficient, and lost samples; the percentage of rejected samples before implementing CAP recommendations was 15.8%, 1.81%, 0.70%, and 0.51% respectively, while after implementing CAP recommendations it was 7%, 0.77%, 0.08%, and 0.05%, respectively. We concluded that the presence of standardized protocol for the pre-analytical activities had improved the quality of samples received by the lab, and we also concluded that accreditation allows laboratories to evaluate their performance, their compliance with the requirements of the accrediting association, and their ability to improve the accuracy of the patient results they provide.

Biological Rhythms of Biochemical Serum Parameters in a Brazilian Population: a Three‐Year Study

A marked decrease in analytical and post-analytical variability has been achieved in clinical laboratories by the use of automated analytical systems. Current studies are now focused on the origin of pre-analytical variability, such as that due to intra-individual differences and biological rhythms. The objective of this work was to evaluate the occurrence of biological rhythms in several biochemical serum parameters in a Brazilian population. A retrospective study (1996 to 1998) was carried out to collect the test results within the reference intervals of adults, from 21 to 50 yr of age (average age of 36 yr) attending the outpatient clinics of the Teaching Hospital at the University of Campinas, São Paulo, Brazil. The reference sample was 52.9% male and 47.1% female and encompassed 15,036 calcium, 7,478 phosphorus, 53,641 urea, 58,315 creatinine and 6,433 uric acid determinations (140,903 in total). Significant annual rhythms were detected in serum calcium (p<or=0.001), with maximum and minimum values in fall and spring, and in serum creatinine (p<or=0.002), with maximum and minimum values in summer and winter. The other parameters did not present significant annual rhythmicity. The seasonal rhythms present in the serum concentrations of calcium and creatinine observed in this large population study, although of small amplitude, should be considered a component of the pre-analytical variation of these clinical laboratory tests.

Preanalytic aspects in postmortem toxicology

The preanalytic phase has been recognized to have a substantial role for the quality and reliability of analytical results, which very much depend on the type and quality of specimens provided. There are several unique challenges to select and collect specimens for postmortem toxicology investigation. Postmortem specimens may be numerous, and sample quality may be quite variable. An overview is given on specimens routinely collected as well as on alternative specimens that may provide additional information on the route of administration, a long term or a recent use/exposure to a drug or poison. Autolytic and putrefactive changes limit the selection and utility of specimens. Some data from case reports as well as experimental investigations on drug degradation and/or formation during putrefaction are discussed. Diffusion processes as well as postmortem degradation or formation may influence ethanol concentration in autopsy specimens. Formalin fixation of specimens or embalmment of the corpse may cause considerable changes of initial drug levels. These changes are due to alterations of the biological matrix as well as to dilution of a sample, release or degradation of the drug or poison. Most important seems a conversion of desmethyl metabolites to the parent drug. Some general requirements for postmortem sampling are given based on references about specimen collection issues, for a harmonized protocol for sampling in suspected poisonings or drug-related deaths does not exist. The advantages and disadvantages of specimen preservation are shortly discussed. Storage stability is another important issue to be considered. Instability can either derive from physical, chemical or metabolic processes. The knowledge on degradation mechanisms may enable the forensic toxicologist to target the right substance, which may be a major break down product in the investigation of highly labile compounds. Although it is impossible to eliminate all interfering factors or influences occurring during the preanalytic phase, their consideration should facilitate the assessment of sample quality and the analytical result obtained from that sample.

Clinical interpretation of reference intervals and reference limits. A plea for assay harmonization

Reference intervals for healthy subjects and diseased populations are important benchmarks for the clinical interpretation of laboratory test values. It is important that the testing conditions used to collect the reference data be closely matched with the testing conditions used for patient data. Interlaboratory differences and intralaboratory changes, especially changes in analytic set-points, can markedly affect the clinical interpretation of tests. If laboratory testing methods could be harmonized, laboratories could potentially share reference data to make these data more reliable.

This chapter illustrates the use of reference intervals for healthy subjects and reference data from diseased populations for medical decisions. One example illustrates the effects of age differences on test result interpretation. Other examples illustrate use of thyroid-stimulating hormone (TSH) and combinations of TSH with free thyroxine measurements for diagnosing thyroid diseases. Both univariate and multivariate reference intervals are discussed. Model systems for using disease prevalence and cost utility functions are provided to illustrate optimization of medical decisions.

Types and frequency of preanalytical mistakes in the first Thai ISO 9002:1994 certified clinical laboratory, a 6 - month monitoring

BACKGROUND: Reliability cannot be achieved in a clinical laboratory through the control of accuracy in the analytical phase of the testing process alone. Indeed a "mistake" can be defined as any defect occuring during the testing process. In the analysis of clinical specimens, there are many possible preanalytical sources of error. Therefore, the application of quality system to laboratory testing requires total quality management throughout the laboratory process, including the preanalytical and postanalytical phases. ISO 9002:1994 is a model for quality assurance in production, installation, and servicing, which includes a number of clauses providing guidance for implementation in clinical laboratories. Our laboratory at King Chulalongkorn Memorial Hospital, the largest Thai Red Cross Society hospital, is the first clinical laboratory in Thailand with ISO 9002:1994 certified for the whole unit. METHOD: In this study, we evaluated the frequency and types of preanalytical mistakes found in our laboratory, by monitoring specimens requested for laboratory analyses from both in-patient and out-patient divisions for 6 months. RESULT: Among a total of 935,896 specimens for 941,902 analyses, 1,048 findings were confirmed as preanalytical mistakes; this was a relative frequency of 0.11 % (1,048/935,896). A total of 1,240 mistakes were identified during the study period. Comparing the preanalytical mistakes to other mistakes in the laboratory process monitored in the same setting and period, the distribution of mistakes was: preanalytical 84.52 % (1,048 mistakes), analytical 4.35 % (54 mistakes), and postanalytical 11.13 % (138 mistakes). Of 1,048 preanalytical mistakes, 998 (95.2%) originated in the care units. All preanalytical mistakes, except for 12 (1.15 %) relating to the laboratory barcode reading machine, were due to human error. CONCLUSION: Most mistakes occurred before samples were analysed, either during sampling or preparation for analysis. This suggests that co-operation with clinicians and personnel outside the laboratory is still the key to improvement of laboratory quality.