Biologic variation of common hematologic laboratory quantities in the elderly

Long-term biological variation estimates of 13 hematological parameters in healthy Chinese subjects

Background The complete blood count (CBC) is a basic test routinely ordered by physicians as a part of initial diagnostic work-up on their patients. To ensure safe clinical application of the CBC, reliable biological variation (BV) data are needed to establish analytical performance specifications. Our aim was to define the BV of CBC parameters using a rigorous protocol that is compliant with the Biological Variation Data Critical Appraisal Checklist (BIVAC) provided by the European Federation of Clinical Chemistry and Laboratory Medicine. Methods Blood samples drawn from 41 healthy Chinese subjects (22 females and 19 males; 23-59 years of age) once monthly for 6 consecutive months were analyzed using an ABX Pentra 80 instrument. The instrument was precisely calibrated. All samples were analyzed in duplicate for 13 CBC parameters. The data were assessed for outliers, normality, and variance homogeneity prior to nested ANOVA. Gender-stratified within-subject (CVI) and between-subject (CVG) BV estimates were calculated. Results The number of remaining data for each subject was 442-484 after removing outliers. No significant differences existed between female/male CVI estimates. Except for leukocytes, neutrophils, and lymphocytes, the mean values of 10 parameters differed significantly between genders, rendering partitioning of CVG data between genders. No significant differences were detected between most BV estimates and recently published estimates representing a Europid population. Conclusions Most BV estimates in BIVAC-compliant studies are similar. The turnover time of blood cells and age distribution of participants should be considered in a CBC BV study. Our study will contribute to global BV estimates and future studies.

30-Year Longitudinal Study of Hematological Parameters of HIV-1 Negative Men Participating in Los Angeles Multicenter AIDS Cohort Study (MACS)

Background

Clinicians often use population-based reference intervals (RIs) when interpreting patient results. However, this method can present problems if the analyte in question has wide variability from person to person.

Methods

We examined the biological variation of routine hematologic markers in 82 white non-Hispanic men every 6 months during a 30-year period, to determine the usefulness of population-based RIs and age-related decline of hematological markers.

Results

Many of these markers showed significant person-to-person differences (index of individuality <1.4 in 10/11 markers) and change over time with a decrease in mean for white blood cells (WBCs), red blood cells (RBCs), hemoglobin, hematocrit, platelets, and neutrophils. The mean increased for monocytes, mean corpuscular volume (MCV), and mean corpuscular hemoglobin (MCH) (all P <.05).

Conclusion

Longitudinal analysis demonstrated significant decline in hematologic marker counts, with the exception of MCV and MCH. Establishment of a personalized baseline for hematologic assessments may be more useful to clinicians than previous methods.

Evaluation of Critical Differences of CEA and CA15.3 Levels in Serial Samples from Patients Operated for Breast Cancer

In the present investigation we evaluated the variability of tumor marker levels in the follow-up of patients without evidence of disease after resection of primary breast cancer. CEA and CA15.3 were measured using commercially available methods in serial blood samples collected from 170 patients. The coefficient of variation among all samples from each patient, which accounts for the total variability (analytical variability + biological variability), was widely scattered (from 4 to 99% for CEA; from 4 to 52% for CA15.3). The critical difference was calculated using the formula designed by Eraser [CD = 2.77. (CVa2 + CVb2)1/2]. It ranged from 11 to 276 for CEA and from 11 to 144 for CA15.3. From the present findings we conclude that:

1) it is possible to identify individually tailored decision criteria to evaluate tumor marker variations in the follow-up of breast cancer patients;

2) in a considerable number of cases the non-tumor-related variability is too high to allow the early identification of minor tumor marker variations that are of clinical relevance.

Short- and medium-term biological variation estimates of red blood cell and reticulocyte parameters in healthy subjects

Background:

The integrated evaluation of traditional and innovative red blood cell (RBC) and reticulocyte parameters is a rapid, inexpensive and non-invasive diagnostic tools for differential diagnosis and follow-up of anemia and other pathological conditions needing bone marrow erythropoiesis assessment. Therefore, estimating the biological variation (BV) of these parameters is essential for evaluating the analytical performance of hematological analyzers, and for enabling accurate data interpretation and appropriate clinical management. This study aims to define short- and medium-term BV estimates and reference change value (RCV) of RBC and reticulocyte parameters.

Methods:

Twenty-one healthy volunteers participated in the assessment of medium-term BV (blood sampling once/week, five consecutive weeks) and 22 volunteers in the assessment of short-term BV (blood sampling once/day, five consecutive days) using Sysmex XN. Outlier analysis was performed before CV-ANOVA, to determine BV estimates with confidence intervals (CI).

Results:

Medium- and short-term within-subject BV were between 0.3% and 16.4% and 0.2%–10.4% (MCH and IRF), respectively, whereas medium and short-term between-subjects BV ranged between 0.9% and 66.6% (MCHC and Micro-R) and 1.4%–43.6% (MCHC and IRF), respectively. The RCVs were similar for all parameters in both arms of the study, except for hemoglobin, RDW-CV and MCV.

Conclusions:

This study allowed for estimating the BV of many RBC and reticulocyte parameters, some of which have not been currently explored. For RBC, hemoglobin, RDW-CV and MCV it seems advisable to use RCV calculated according to monitoring time and/or differentiated by sex. As regards analytical goals, we suggest using the most stringent targets found in the short-term arm of this study.

Spot Sample Urine Specific Gravity Does Not Accurately Represent Small Decreases in Plasma Volume in Resting Healthy Males

BACKGROUND

Urine specific gravity (U_SG) is often used to assess hydration status, particularly around athletic competition, but it is unknown whether high U_SG is indicative of plasma volume (PV) reduction (i.e., hypohydration). We tested the hypothesis that if high U_SG is reflective of reduced PV, subsequent fluid ingestion would increase PV.

PURPOSE

The purpose of this study was to examine 24-hour changes in U_SG and PV in individuals presenting with high and low spot U_SG.

METHODS

Nineteen healthy males were provided food and water over 24 hours with a total water volume of 35 ml·kg^-1 body mass. Absolute PV and blood volume (BV), measured using the CO-rebreathe technique, along with U_SG were measured before and after a 24-hour intervention period. Based on a preintervention morning spot U_SG, subjects were post hoc assigned to groups according to U_SG (≤1.020 or >1.020; low and high U_SG, respectively).

RESULTS

Despite presenting with an elevated spot U_SG (1.026 ± 0.004), subsequent fluid ingestion over 24 hours did not lead to changes (∆) in PV (-75 ± 234 ml) or BV (-156 ± 370 ml) in the high U_SG group (p > 0.05). However, a spot U_SG after the 24-hour intervention in this group decreased (p = 0.018) to a level indicating improved hydration status (1.017 ± 0.007). In the low U_SG group, there were no changes in PV (-39 ± 274 ml), BV (-82 ± 396 ml), or U_SG (0.003 ± 0.007) over the 24-hour fluid intervention (all p > 0.05).

CONCLUSIONS

Despite a high preintervention U_SG and subsequent decrease after 24-hour fluid intake, measures of PV and BV were not indicative of this seemingly improved hydration status. This suggests that a highly concentrated spot sample U_SG and subsequent changes are not accurately representative of PV or BV.

Within-day biological variation and hour-to-hour reference change values for hematological parameters

BACKGROUND

Middle- and long-term biological variation data for hematological parameters have been reported in the literature. Within-day 24-h variability profiles for hematological parameters are currently lacking. However, comprehensive hour-to-hour variability data are critical to detect diurnal cyclical rhythms, and to take into account the 'time of sample collection' as a possible determinant of natural fluctuation. In this study, we assessed 24-h variation profiles for 20 hematological parameters.

METHODS

Blood samples were collected under standardized conditions from 24 subjects every hour for 24 h. At each measurement, 20 hematological parameters were determined in duplicate. Analytical variation (CVA), within-subject biological variation (CVI), between-subject biological variation (CVG), index of individuality (II), and reference change values (RCVs) were calculated. For the parameters with a diurnal rhythm, hour-to-hour RCVs were determined.

RESULTS

All parameters showed higher CVG than CVI. Highest CVG was found for eosinophils (46.6%; 95% CI, 34.9%-70.1%) and the lowest value was mean corpuscular hemoglobin concentration (MCHC) (3.2%; 95% CI, 2.4%-4.8%). CVI varied from 0.4% (95% CI, 0.32%-0.42%) to 20.9% (95% CI, 19.4%-22.6%) for red cell distribution width (RDW) and eosinophils, respectively. Six hematological parameters showed a diurnal rhythm.

CONCLUSIONS

We present complete 24-h variability profiles for 20 hematological parameters. Hour-to-hour reference changes values may help to better discriminate between random fluctuations and true changes in parameters with rhythmic diurnal oscillations.

Biological variation of platelet parameters determined by the Sysmex XN hematology analyzer

BACKGROUND

This study was aimed to define the short- and medium-term biological variation (BV) estimates, the index of individuality and the reference change value (RCV) of platelet count, platelet distribution width, mean platelet volume, platelet larger cell ratio, plateletcrit and immature platelet fraction.

METHODS

The study population consisted of 43 health subjects, who participated to the assessment of medium-term (21 subjects; blood sampling once a week for 5 consecutive weeks) and short-term (22 subjects; blood sampling once a day for 5 consecutive days) BV study, using Sysmex XN-module. Eight subjects were also scheduled to participate to both phases. The data were subject to outlier analysis prior to CV-ANOVA, to determine the BV estimates with the relative confidence intervals.

RESULTS

The medium-term and short-term within-subject BV (CV_I) was comprised between 2.3 and 7.0% and 1.1-8.6%, whereas the medium-term and short-term between-subjects BV (CV_G) was comprised between 7.1 and 20.7% and 6.8-48.6%. The index of individuality and index of heterogeneity were always respectively <0.6 and >0.63 for all the parameters, in both arms of the study. The RCVs were similar for all parameters, in both arms of the study.

CONCLUSION

This study allowed to define the BV estimates of many platelet parameters, some of them unavailable in literature. The kinetics of platelet turnover suggests the use of short-term BV data for calculating analytical goals and RCV. The correct clinical interpretation of platelet parameters also necessitates that each laboratory estimates local RCV values.

Derivation of level-specific reference change values (RCV) from a health screening database and optimization of their thresholds based on clinical utility

BACKGROUND

Reference change values (RCV) are used for judging the significance of changes between any two measurements. Based on the within-individual CV (CVI), RCV is conventionally computed as the 95% confidence limit (CL) of the changes: RCV=1.96×2CVI. $RCV = 1.96 \times \sqrt 2 C{V_I}.$ However, the appropriateness of assuming a constant CVI and using the 95% CL for RCV remains controversial.

METHODS

The level-specific CVI and RCV were estimated for 20 screening tests using a database composed of results from 13,545 health-screening attendees over a 17-year period, after preliminary exclusion of individuals taking medications or having unusual changes in body mass index (BMI). A rational CL for RCV was explored in reference to a clinical score for the metabolic syndrome, sMS, which was derived based on a logistic regression model consisting of tests related to metabolic syndrome. The effect of adjusting CL for the RCV on diagnostic efficacies of detecting between-year change in sMS was evaluated.

RESULTS

Test level dependency of CVI was apparent for some screening tests which have distributions with prominent skewing. The use of level-specific RCV was thus essential for them. The sensitivity for detecting a critical change in sMS based on the RCV set at 95%CL was extremely low in the majority of tests. However, by lowering CL stepwise from 95 to 75%, the sensitivity improved greatly without much change in specificity and positive predictive value. Loss-and-gain analysis showed that CL for RCV set around 80% gave the lowest loss, assuming a policy of reducing false negative judgment.

CONCLUSIONS

Level specific CVI and RCV were necessary in tests with skewed distributions. RCV using 80%-90% CL is suitable in health screening for diseases that require early intervention for changes.

Laboratory diagnosis of anemia: are the old and new red cell parameters useful in classification and treatment, how?

INTRODUCTION

Anemia is a global problem affecting the population in both developing and developed countries, and there is a debate on which hemoglobin level limit should be used to define anemia in general population and particularly in the elderly. We present herein a laboratory approach to diagnosing the possible causes of anemia based on traditional and new erythroid parameters. In this article, we provide practical diagnostic algorithms that address to differential diagnosis of anemia. Based on both morphological and kinetic classifications, three patterns were considered: microcytic, normocytic, and macrocytic.

METHODS

Main interest is on the clinical usefulness of old and new parameters such as mean cell volume (MCV), red blood cell distribution width (RDW), hypochromic and microcytic erythrocytes, immature reticulocyte fraction (IRF), and some reticulocyte indices such as reticulocyte hemoglobin content and mean reticulocyte volume. The pathophysiologic basis is reviewed in terms of bone marrow erythropoiesis, evaluated by reticulocyte count (increased or normal/decreased) and IRF. The utility of reticulocyte indices in the diagnosis of iron-deficient erythropoiesis (absolute or functional) and in monitoring of response to treatment in nutritional anemia (iron and cobalamin) was also investigated.

RESULTS

For each parameter, the availability, the possible clinical applications, and the limitations were evaluated. A discussion on intraindividual biological variation and its implication on the usefulness of conventional reference intervals and in longitudinal monitoring of the patients was also reported.

CONCLUSION

Red cell parameters and reticulocyte indices play an essential role in differential diagnosis of anemia and in its treatment. More efforts are needed in harmonizing parameters whose results are still too different when produced by different analyzers.

Central tendency and variability in biological systems

In this article, the author reviews the manner in which researchers characterize data. Normality, standard deviation, mean, and other concepts related to parametric statistics are discussed in common language, with a minimum of jargon and with clinical examples.

Quality control of automated cell counters

The hematology analyzers of today provide more reproducible analyses compared with those of a few decades ago, necessitating an evolution in hematology quality practices. The improved performance allows use of simple quality control rules. This improved performance also renders the repeat analysis of critical value specimens non value added. Some of the patient averaging techniques have become outmoded and need to be replaced by less complicated calculations but with truncation of predictable outlying populations. The ready availability of comparative peer quality control values helps to improve analyzer precision and accuracy, and simplifies instrument validation and calibration.

Biological variations of ADAMTS13 and von Willebrand factor in human adults

Background:

The ultra-large von Willebrand factor (vWF) multimers are very active and must be degraded by ADAMTS13 for optimal activity. A severe functional deficiency of ADAMTS13 has been associated with thrombotic thrombocytopenic purpura. The correct interpretation of patient vWF and ADAMTS13 plasma levels requires an understanding of the biological variation associated with these analytes. In the present paper, we aimed to determine the biological variation of ADAMTS13 and vWF in human adults.

Materials and methods:

Blood samples were collected weekly from 19 healthy subjects for 5 consecutive weeks. vWF activity and antigenicity were determined using aggregometric and immunoturbidimetric methods. ADAMTS13 antigenicity and activity were determined by ELISA.

Results:

The within-subject biological variations for vWF activity and antigenicity were 8.06% and 14.37%, respectively, while the between-subject biological variations were 18.5% and 22.59%, respectively. The index of individuality for vWF activity was 0.44, while vWF antigenicity was 0.64. Similarly, ADAMTS13 activity and antigenicity within-subject biological variations were 12.73% and 9.75%, respectively, while between-subject biological variations were 9.63% and 6.28%, respectively. The ADAMTS13 indexes of individuality were 1.32 and 1.55, respectively.

Conclusion:

We report high biological variation and individuality in vWF antigenicity and activity levels. However, ADAMTS13 antigenicity and activity displayed high biological variation, but low individuality. Thus, population-based reference intervals may be useful for monitoring ADAMTS13 antigenicity and activity, but not for vWF, which displays high individuality. These findings should be considered when determining the reference interval and other clinical variables associated with ADAMTS13 and vWF levels.

Hematology and serum chemistry values of sooty mangabeys (Cercocebus atys): comparison with rhesus monkeys

BACKGROUND

The sooty mangabey is a vulnerable West African species that naturally harbors simian immunodeficiency virus (SIV) without pathological symptoms. We present normative hematology and serum chemistry values for this species.

METHODS

Hematology analytes from 136 females and 96 males and serum chemistry analytes from 57 females and 26 males were studied.

RESULTS

Values of several analytes fell outside published reference ranges in the rhesus monkey, a laboratory standard for Old World primates. Erythrocyte-related parameters were higher in mangabeys than in rhesus monkeys, while platelet counts were lower. Mangabeys also had higher gamma-glutamyltransferase levels and lower urea nitrogen levels. Males had higher erythrocyte-associated values than females. Albumin, globulin, albumin/globulin ratio, calcium, and creatinine changed with age in patterns similar to those reported for the rhesus monkey.

CONCLUSIONS

The unique blood profile of the mangabey should be taken into account in clinical and experimental studies of this species.

Biological variation and reference change values of common clinical chemistry and haematologic laboratory analytes in the elderly population

BACKGROUND

Biological variation (BV) and reference change values (RCVs) have been widely described for the general population, but the use of these data derived from adults in the elderly population is a controversial issue. We determined the within- and between-subject BV and RCV in both elderly and young people and compared them with previously published analyses.

METHODS

Samples were collected from 135 volunteers over 80 years of age at weekly intervals over 4 weeks. Eighteen biochemical and eight haematological analytes were measured. The Fraser and Harris methods were used to calculate the components of BV and RCV. To perform a comparative analysis, a reference group of 118 young subjects was studied under the same conditions.

RESULTS

The obtained coefficients of BV showed statistical differences in many cases, but in general, both the elderly and young patient data fall within the ranges previously described for the general population. The indexes of individuality for the analytes investigated did not exceed 1.4 in any case and were <0.6 for some analytes. The RCVs derived from elderly subjects were similar to those published in the young population, both in healthy and diseased individuals.

CONCLUSIONS

The strong individuality observed supports the preferential use of RCVs rather than population-based reference intervals in elderly people. For most of the analytes studied, data from the young population can be applied to elderly people, but the specific elderly coefficients of BV and RCVs are a recommended option.

Biological Variations of Hematologic Parameters Determined by UniCel DxH 800 Hematology Analyzer

Context.—The Coulter DxH 800 hematology analyzer can determine conventional hematologic parameters. It also provides many new hematologic parameters, some of which show potential clinical utility.

Objectives.—To study, for the first time, the biological variations of new hematologic parameters and reinvestigate the biological variations of conventional hematologic parameters using the newest Coulter hematology analyzer.

Design.—Forty adult volunteers (21 women and 19 men) were included. All participants maintained their normal lifestyles. Blood samples were drawn in duplicate by a single experienced phlebotomist and analyzed within 2 hours using a single analyzer. Before each batch analysis, the instrument quality controls were performed using the same lots of reagents.

Results.—Within-subject and between-subject biological variations for the conventional hematologic parameters were compatible with published data. The analytic variation of the DxH 800 for these parameters appeared smaller. Index of individuality (ratio of within-subject to between-subject biological variation) for all parameters was low. In addition, intraday and interday biological variations of most parameters studied are fairly constant among the population examined.

Conclusions.—These observations are clinically valuable. Data on within-subject biological variation and analytic precision may be used to generate objective delta-check values for use in quality management. Comparing within-subject and between-subject biological variation on new parameters may allow us to decide the utility of traditional population-based reference ranges. Furthermore, documentation of biological variations of new parameters is an essential prerequisite in the development of any clinical application in the future.

Determination of blood volume by pulse CO-oximetry

The objective of this study was to determine whether changes in carboxyhaemoglobin (COHb) saturation following carbon monoxide (CO) rebreathing can be accurately detected by pulse CO-oximetry in order to determine blood volume. Noninvasive measurements of carboxyhaemoglobin saturation (SpCO) were continuously monitored by pulse CO-oximetry before, during and following 2 min of CO rebreathing. Reproducibility and accuracy of noninvasive blood volume measurements were determined in 16 healthy non-smoking individuals (15 males, age: 28 ± 2 years, body mass index: 25.4 ± 0.6 kg m(-2)) through comparison with blood volume measurements calculated from invasive measurements of COHb saturation. The coefficient of variation for noninvasive blood volume measurements performed on separate days was 15.1% which decreases to 9.1% when measurements were performed on the same day. Changes in COHb saturation and SpCO following CO rebreathing were strongly correlated (r = 0.90, p < 0.01), resulting in a significant correlation between invasive and noninvasive blood volume measurements (r = 0.83, p = 0.02). Changes in SpCO following CO rebreathing can be accurately detected by pulse CO-oximetry, which could potentially provide a simplified, convenient and reproducible method to rapidly determine blood volume in healthy individuals.

Patient-specific measures of a biomarker for the generation of individual reference intervals: hemoglobin as example

Although hemoglobin concentration measurement is among the most commonly performed blood tests, the description of global population parameters, heterogeneous factors, and within-subject variations in patients with disease remains incomplete. As absolute action values are being published in the medical literature and by government healthcare agencies, these measures are important to define patient-specific ranges of biomarkers. Here, a global clinical trial data set composed of 1,537,932 hemoglobin values from 416,374 patients and 372 clinical indications was generated over 2 years by automated analyzers in a global network of 5 laboratories. Within- and between-subject components of variance and the effect of factors age, gender, nationality, and clinical indication were determined using unbalanced multiway analysis of variance. Average within-subject variances differed significantly depending on the clinical indication (0.15-1.3 g(2)/dL(2)) but, nevertheless, remained significantly lower than between-subject variances. The main sources of between-subject variation were clinical indication and gender, followed by age and nationality. An adaptive Bayesian approach was then used to generate patient-specific ranges of hemoglobin for drug safety and efficacy assessment in clinical trials. The same methodology can be applied to the evaluation of any biomarker signal in translational medicine.

Functional assessment of cellular non-specific and specific immunity in selected healthy elderly

Thirteen healthy elderly were selected according to a simplified SENIEUR admission protocol including clinical, hematological and biochemical parameters. The goal of this protocol was to limit the influence of diseases and/or medications on the assessment of immune functions in the elderly. Plasma zinc levels of healthy elderly were comparable to those of young subjects. Cellular nonspecific immunity was determined by measuring chemiluminescence (CL) of peripheral blood granulocytes activated by opsonized zymosan particles. CL of granulocytes from healthy elderly was delayed in comparison to that of young controls when autologous serum was used. Lymphocyte proliferation induced by phytohemagglutinin-P (PHA-P) or zinc chloride (ZnCl(2)) in a serum free medium was lower in the elderly than in young controls. Preincubation of lymphocytes with ZnCl(2) before PHA-P stimulation did not restore the impaired proliferative activity of cells from old donors.

Quality assurance in clinical laboratories. An updated supplement to a bibliography

A supplement to a bibliography (Scand J Clin Lab Invest 1987;47 suppl. 187:1-96) dealing with quality assurance in the clinical laboratory is presented. The increasing role of national and international standardizing bodies is stressed as well as implementation of rules of "good laboratory practice". Objectively established quality goals for all services is highly needed in order to provide a rationale for the efforts dedicated to quality improvements. Quality goals for many clinical chemistry and haematology investigations are now available.

Practical experience with a quality control procedure using retained patient specimens on Technicon H1 and COULTER S 880

External quality assessment and internal quality control in hematology is complicated by the lack of good control materials. Commercial materials do not always behave as patient blood and they are expensive. Patient specimens are unstable, but may be used either within certain time limits or as in Bull's moving average for red cell indices. We have used retained patient specimens for internal quality control supplemented by a commercial control material. Three patient-specimens were run alternatively on a Technicon H1 and a Coulter 880 at regular intervals. The variations for each instrument and between instrument were computed. We used the 2 of 3 (2s) control rule. Our conclusion is that the Coulter 880 had an overall better performance than the Technicon H1 when using retained patient specimens. But both instruments practically met suggested analytical goals.

Analytical goals for haematology tests

All analytical methods can be defined in terms of their practicability and reliability performance characteristics. Desirable standards of performance, or analytical goals, are required for these, particularly for imprecision and inaccuracy. Goals for imprecision have been set using a variety of methods including reference values, opinions of clinicians, views of individuals, and data on biological variation. The last approach is currently favoured; desirable imprecision is equal to or less than one-half of the biological within-subject variation. If this goal is met, total variability of test results is increased by less than about 10% due to analytical variability. Valid estimates of within-subject variability are available for the complete blood count. The goal for inaccuracy is that methods should have no bias so that results are comparable over time and geography; goals based on biological variation should be viewed and used, therefore, as goals for total error. In current practice, some of the goals cannot be met; they should be considered as targets worthy of achievement, not as inflexible criteria of acceptance or rejection of methods.

Influence of age on the stability of human erythrocyte membranes

This work evaluated the dependence of erythrocyte membrane stability on age, temperature (26, 32, 37, 42 and 47 degrees C), nutritional status, red cell count, red cell distribution width (RDW) and mean corpuscular volume (MCV) in human females (n = 67, 20-94 years). Erythrocyte membrane resistance to hypotonic lysis was expressed as the NaCl concentration (H(50)) capable of promoting 50% haemolysis. A nutritional evaluation was performed using the Mini Nutritional Assessment (MNA) instrument, which showed that 76.1% of the study group were well nourished and 23.9% were at risk of malnutrition. H(50) demonstrated a negative correlation with age at all temperatures. H(50) showed no correlation with either MNA scores or with any haematological indices. The power and significance of the correlations improved when we censored from the analyses those individuals at risk of malnutrition. The thermal dependencies lines for H(50) demonstrated higher values for females 20-39 years of age compared with those more than 60 years of age. These results suggest that erythrocyte resistance to hypotonicity (erythrocyte membrane stability), increased with age of study volunteers. This increased stability was more pronounced among well-nourished individuals.

Blood transfusions in athletes. Old dogmas, new tricks

Blood doping consists of any illicit means used to increase and optimize oxygen delivery to the muscles and includes blood transfusions, administration of erythropoiesis-stimulating substances, blood substitutes, natural or artificial altitude facilities, and innovative gene therapies. The use of blood transfusion, an extremely straightforward, practical and effective means of increasing an athlete's red blood-cell supply in advance of competition, became rather popular in the 1970s, but it has suddenly declined following the widespread use of recombinant human erythropoietin among elite endurance athletes. Most recently, following implementation of reliable tests to screen for erythropoiesis-stimulating substances, blood transfusions have made a strong resurgence, as attested by several positive doping tests. Doping by blood transfusion can be classified as homologous, where the blood is infused into someone other than the donor, and autologous, where the blood donor and transfusion recipient are the same. The former case produces more clinically relevant side effects, but is easily detectable using current antidoping protocols based on erythrocyte phenotyping by flow cytometry and, eventually, erythrocyte genotyping by DNA testing. Since the donor and recipient blood are identical in autologous blood doping, this is less risky, though much more challenging to detect. Indirect strategies, relying on significant deviations from individual hematological profiles following autologous blood donation and reinfusion, are currently being investigated. For the time being, the storage of athletes' blood samples to allow testing and sanctioning of guilty athletes once a definitive test has been introduced may represent a reliable deterrent policy.

Errors of measurement for blood volume parameters: a meta-analysis

The volume of red blood cells (V(RBC)) is used routinely in the diagnostic workup of polycythemia, in assessing the efficacy of erythropoietin administration, and to study factors affecting oxygen transport. However, errors of various methods of measurement of V(RBC) and related parameters are not well characterized. We meta-analyzed 346 estimates of error of measurement of V(RBC) for techniques based on Evans blue (V(RBC,Evans)), 51chromium-labeled red blood cells (V(RBC,51Cr)), and carbon monoxide (CO) rebreathing (V(RBC,CO)), as well as hemoglobin mass with the carbon-monoxide method (M(Hb,CO)), in athletes and active and inactive subjects undergoing various experimental and control treatments lasting minutes to months. Subject characteristics and experimental treatments had little effect on error of measurement, but measures with the smallest error showed some increase in error with increasing time between trials. Adjusted to 1 day between trials and expressed as coefficients of variation, mean errors for M(Hb,CO) (2.2%; 90% confidence interval 1.4-3.5%) and V(RBC,51Cr) (2.8%; 2.4-3.2%) were much less than those for V(RBC,Evans) (6.7%; 4.9-9.4%) and V(RBC,CO) (6.7%; 3.4-14%). Most of the error of V(RBC,Evans) was due to error in measurement of volume of plasma via Evans blue dye (6.0%; 4.5-7.8%), which is the basis of V(RBC,Evans). Most of the error in V(RBC,CO) was due to estimates from laboratories with a relatively large error in M(Hb,CO), the basis of V(RBC,CO). V(RBC,51Cr) and M(Hb,CO) are the best measures for research on blood-related changes in oxygen transport. With care, V(RBC,Evans) is suitable for clinical applications of blood-volume measurement.

Association of single nucleotide polymorphisms in the thrombopoietin-receptor gene, but not the thrombopoietin gene, with differences in platelet count

Little is known about the mechanisms explaining the wide variation in platelet counts (PLT) and other hematologic parameters in humans. We previously showed that the sex-based difference in hematocrit was associated with nucleotide variation in the erythropoietin receptor gene (EPOR). We sought to identify new polymorphisms of the human thrombopoietin (TPO) and thrombopoietin receptor (TPOR) genes to determine any associations with blood PLT counts. We screened TPO and TPOR for polymorphisms using single-strand conformation polymorphism (SSCP) and DNA sequencing. Association of polymorphisms was studied in 304 normal subjects with low or high PLT counts. Distribution of allelic frequency was analyzed by the Chi-square statistic. Single nucleotide polymorphisms (SNPs) with two alleles were found in TPO and TPOR. The TPO SNP was a G to A transition at nucleotide 5753, and the TPOR SNP was a C to A transversion at position 550 in the 5'-promoter area. The allelic frequencies were 0.54 for G and 0.46 for A of TPO, and 0.62 for C and 0.38 for A of TPOR in a Caucasian population. The frequency of the TPOR allele "C" was significantly higher in subjects with high PLT count (>258 k/mm3) versus low PLT count (<224 k/mm3) and in males with high PLT count (>258 k/mm3) versus males with low PLT count (<212 k/mm3). In contrast, the frequency of the TPO alleles was not related to blood PLT counts. An association of TPO and TPOR allele distribution to red and white blood cell parameters was seen. These new SNPs found for the human TPO and TPOR genes help explain variations in blood PLT counts and may be useful in patient studies related to the roles of TPO and/or TPOR in disease.

Biological variation of soluble CD163

A soluble plasma form of CD163 (sCD163) was recently identified. The protein has anti-inflammatory effects in vitro and is elevated in patients with myelo-monocytic leukaemia and infection. For rational use and evaluation of this potential new quantity it is important to have knowledge of its biological variability and to use a methodology that has a sufficiently analytical quality. The day-to-day and diurnal biological variabilities of sCD163 were studied in 12 healthy people using a sandwich ELISA. The within-run-, between run- and total analytical coefficients of variation were estimated to 3.6%, 4.8% and 6.0%, respectively. The day-to-day within-subject biological variation was estimated to 9.0%, and the between-subject biological variation to 35.9%. A diurnal variation in sCD163 concentrations with 14% lower values in the night (supine position) was observed. The ratio between total analytical variation and within-subject biological variation was 0.67. The index of individuality, calculated as the ratio between within-subject biological variation and between-subject biological variation, was low and similar to complement factors and immunoglobulins. A low index of individuality is important in a monitoring situation where small changes from the set point of the individual can be detected in serial measurements. For this purpose, the critical difference for a series of results in the same patient (significant at p < 0.05) was calculated to 30% for samples taken on different days and measured in separate runs.

Haematocrit: within-subject and seasonal variation

This review was undertaken, concerning within-subject biological variation and seasonal variation of haematocrit in normal healthy adults and athletes, to find the limits for natural, intra-individual variation in haematocrit values. The terminology and calculations followed well defined theories, from the field of laboratory medicine, about biological variation. Based on results from 12 studies of 638 normal healthy adults, and which used a sampling interval of 1 day to 1-2 months, the coefficient of within-subject biological variation of haematocrit is 3%. The normal within-subject biological variation (3%) and analytical variation (3%) may explain a relative change of approximately 12% (95% level) [e.g. a change from 0.42-0.47] between two successive haematocrit values, measured with a time interval between 1 day and 1-2 months, in a normal healthy adult. Partly due to haemodilution in warm weather, haematocrit often has a seasonal variation in normal healthy adults; based on results from 18 studies of 24 793 participants, the population mean is approximately 3% lower in summer than winter. Population mean values that are 7% lower in summer than winter have been found in some studies, although no seasonal effect may also be seen, especially in temperate climates. If haematocrit values are sampled at yearly peak and trough time points, with intervals of up to 6 months, a 15% relative change (95% level) can be seen in a normal healthy adult; e.g. a change from 0.42-0.48. Published values for haematocrit in athletes are scarce. It is known that the haematocrit value is influenced by training, especially in the first weeks before a new steady-state is reached. Theoretically, the biological variation in athletes could therefore be greater than in normal individuals. Based on two references addressing the biological variation of haematocrit in athletes, however, the above results are also valid for athletes. Further studies, both in the short term and throughout the seasons, are recommended about the natural variation of haematocrit in athletes.

Anti-beta2-glycoprotein I ELISA: methodology, determination of cut-off values in 434 healthy Caucasians and evaluation of monoclonal antibodies as possible international standards

Antibodies against beta2-glycoprotein I are among the most commonly detected subset of antiphospholipid antibodies. The inter-laboratory comparability of results is hardly possible due to methodological differences, lack of international standards and different cut-off values. We evaluated an ELISA for the detection of anti-beta2-glycoprotein I using the analytical goals based on biological variations for similar analytes (immunoglobulins). By our ELISA we fulfilled the optimal (IgA, IgM) or minimal (IgG) analytical goals in long-term imprecision. The determination of cut-off values was based on the frequency distribution of results obtained on 434 healthy Caucasians. To aim at a better inter-laboratory comparability we tested two monoclonal antibodies as possible calibrators: HCAL (IgG) and EY2C9 (IgM). Binding properties determined by dilutional curves showed great similarities with polyclonal sera, used as in-house standards. Cut-off values were expressed by concentrations of IgG and IgM monoclonal antibodies (4.5 and 25.3 microg/l). Our study shows the possibility for a successful application of analytical goals based on biological variation even when data for a particular analyte are not available. The expression of cut-off values, obtained on a large scale Caucasian population, by the concentration of IgG and IgM monoclonal antibodies could make possible a more reliable inter-laboratory comparison of data.

Laboratory screening for erythropoietin abuse in sport: an emerging challenge

The growing diffusion of banned practice to improve the athletic performances is forcing clinical laboratories to identify and standardize reliable assays to detect potential unfairness. Among the doping practices, the use of recombinant human erythropoietin is becoming fairly popular, due to simplicity and safeties of administration and troublesome detection. The heterogeneous response rate, the presence of a little but significant amount of naturally occurring hormone, the short half-life exhibited by recombinant human erythropoietin and the lack of standardization of commercial assays appear the main problems to overcome. Aim of the present article is to provide a critical review of some of the more widespread laboratory techniques currently available for the screening for erythropoietin abuse in sport.

Aging and red blood cell membrane: a study of centenarians

Successful aging, characterized by little or no loss in physiological functions, should be the usual aging process in centenarians. It is known that well-preserved physiological functions depend on the proper functioning of cell systems. In this article we focus on cell membrane integrity and study the red blood cell membrane to evaluate the effect of physiological aging in centenarians. Fifteen healthy, self-sufficient centenarians, mean age 103 years, were examined by assessing hemocytometric values and some relevant characteristics of the erythrocyte membrane, i.e., the cholesterol/phospholipid molar ratio, the distribution of phospholipid classes and their fatty acid composition, the integral and skeletal protein profiles. The centenarians showed a significant decrease in the red blood cell count (p < 0.0002), hemoglobin (p < 0.0002), and hematocrit (p < 0.0005). The red blood cell membrane showed a significantly increased cholesterol/phospholipid molar ratio (p < 0.01), with a concomitant increase in polyunsaturated fatty acids in phosphatidylcholine (p < 0.001) and, to a lesser extent, in phosphatidylethanolamine. The electrophoretic pattern of membrane proteins was qualitatively normal compared to controls but the densitometric analysis showed a significant increase in the integral protein band 4.2 (p < 0.05) and in the skeletal protein actin (p < 0.001). Extreme longevity seems to be associated with a substantial integrity of the erythrocyte membrane. Moreover, the evident increase in polyunsaturated fatty acids and in actin are likely to improve the membrane fluidity and to strengthen the membrane structure.

When to collect blood specimens: midmorning vs fasting samples

This study was carried out to define the consequences of collecting blood specimens during the forenoon instead of using fasting specimens collected early in the morning. Extensive laboratory data were obtained from specimens collected from fasting participants at 0800, after breakfast at 0930, and again at 1100. The subjects were inpatients in medical and surgical wards (n = 51; 13 women and 38 men; ages, 32–87 years) and subjectively healthy volunteers corresponding to outpatients (n = 51; 31 women and 20 men; ages, 18–63 years). The coefficient of variation (CV, %) of the patient results was compared with the analytical CV. The observed CVs of the subjects’ results far exceeded the analytical CV (%), the average being 3.5-fold and up to 14-fold for some analytes. In individual results the observed change often exceeded the medically derived clinical critical difference. Laboratory data should always be interpreted in the context in which they were obtained. Clinical decisions should be based on objective data (observations) more than on experience and educated guesses. Different medical specialities and different clinical situations may require different kinds of procedures.

Within-subject biological variation of reticulocytes and reticulocyte-derived parameters

Automation of reticulocyte counting has decreased the analytical imprecision of this parameter. This has made it possible to use the number of reticulocytes and its derived parameters (reticulocyte maturity and reticulocyte cell indices) in new diagnostic and monitoring situations. For rational use of these parameters, it is important to have knowledge of their biological variability. The biological variability of reticulocytes and its derived parameters was studied in 13 healthy people during a period of 7 wk on 2 different instruments. The within-subject coefficient of variation for the reticulocyte count was about 11%, for the mean reticulocyte volume, mean reticulocyte haemoglobin content and mean reticulocyte haemoglobin concentration it was between 1 and 2%, whereas the coefficient of variations for the subpopulations of reticulocytes with different maturity varied depending on the method used for the measurements. The critical difference, that is the change in a result making it significantly different from the previous result, was about 35% for the reticulocyte count and 5-8% for the reticulocyte cell indices, making these indices excellent to follow changes in erythropoiesis. With a possible exception for the mean reticulocyte volume, the within-subject variation was small compared to the between-subject variation.

Study on long-term biological variability of erythrocyte sedimentation rate

The aim of the study was the estimation of long-term within-subject variability of ESR. ESR was measured in 52 healthy persons of both sexes, aged 20-50 years, twice a month during 6 consecutive months, after the method of Westergren. The within-run imprecision, expressed as CV was 13.2% (mean value, x = 3.9 mm h-1) and 3.8% (x = 16.0 mm h-1) respectively. The analytical day-to-day imprecision, calculated by duplicate measurements during 23 consecutive days. was s = 0.6 mm h-1. The medians from within-subject variances were 0.9 for men and 8.6 for women, respectively. The 90th percentiles were 11.3 for men and 40.6 for women, respectively. The critical differences based on the median value (dk50) were 3.1 mm h-1 (men) and 8.3 mm h-1 (women). The critical differences based on the 90th percentile (dk90) are 9.5 mm h-1 (men) and 17.7 mm h-1 (women).

Age-related changes in laboratory test results. Clinical implications

Many quantities assayed in clinical laboratories demonstrate age-related changes. Particularly important periods are early life, adolescence, old age, and after the menopause in females. The changes that occur until adulthood are well documented. Fewer data are available on elderly people even though they consume a large component of healthcare resources. In diagnosis, and prior to initiation of drug therapy, when no previous results are available, reference values must be available to aid interpretation. Reference intervals generated from elderly people are sometimes wider than in younger adults. It is suggested that conventional adult reference values should be used in general for the very elderly since, at least in part, the wider intervals are probably due to inclusion of individuals who are unhealthy in the reference sample group. Most quantities have marked individuality, and serial values for an individual span only a part of the reference interval. Individuals can have values which are very unusual for them but still lie within the reference limits; this implies that clinical laboratory tests will be less than ideal in the detection of latent or early disease. The average within-subject variation in healthy elderly people and younger adults is similar. Therefore, the large database on biological variation can be used, with analytical imprecision, to calculate critical differences for serial results in an elderly individual which must be exceeded before significance can be claimed. These critical differences are of value in monitoring the effects of drug therapy.

Clinical goals for measurement of hemoglobin in primary care as assessed by paper vignettes

A random sample of 10% (273) Norwegian general practitioners (GP) received a questionnaire including 11 case stories. For each case the GP was asked to fill in an action value for hemoglobin which should represent the minimal change considered necessary by that general practitioner to take action towards the patient. These minimal changes could then be used for calculation of imprecision goals assuming that there was no change in the bias of the two measurements. The analytical imprecision goals (CV) derived from the different case stories varied between 0% and 7.8% with a mean of 2.8% accepting a false positive rate of 5%. The GPs assessment of a single case story also varied substantially.

Biological variation of the leukocyte differential count quantities

The biological variation of the blood concentration and number fraction of the different kinds of leukocytes have been estimated, over a one-year period in a group of 19 women and 20 men, apparently healthy volunteers. All measurements have been performed with a Toa E-5000 haematological analyser. The medians of the within-subject biological coefficients of variation, separated by sex when significant differences exist, are the following for concentrations: 9.4% in men and 15.4% in women for the leukocytes, 16.9% in men and 26.9% in women for the neutrophils, 12.3% for the lymphocytes, 14.9 for the basophils+eosinophils+monocytes (as measured by Toa E-5000); and for number fraction are the following: 8.6% for neutrophils, 0% in men and 7.2% in women for lymphocytes, and 16.7 for basophils+eosinophils+monocytes (as measured by Toa E-5000). With these data the index of individuality, the critical difference for significant change detection and the desirable imprecision have been calculated.