Accuracy of predonation Hct sampling affects donor safety, eligibility, and deferral rates

From Unit to Dose: A Machine Learning Approach for Precise Prediction of Hemoglobin and Iron Content in Individual Packed Red Blood Cell Units

Transfusion of packed red blood cells (pRBCs) saves lives, but iron overload limits survival of chronically transfused patients. Quality control methods, which involve entering pRBC units and removing them from the blood supply, reveal that hemoglobin (38.5-79.9 g) and heme iron (133.42-276.89 mg) vary substantially between pRBCs. Yet, neither hemoglobin nor iron content can be quantified for individual clinically used pRBCs leading to rules of thumb for pRBC transfusions. Keeping their integrity, the authors seek to predict hemoglobin/iron content of any given pRBC unit applying eight machine learning models on 6,058 pRBCs. Based on thirteen features routinely collected during blood donation, production and quality control testing, the model with best trade-off between performance and complexity in hemoglobin/iron content prediction is identified. Validation of this model in an independent cohort of 2637 pRBCs confirms an adjusted R² > 0.9 corresponding to a mean absolute prediction error of ≤1.43 g hemoglobin/4.96 mg iron (associated standard deviation: ≤1.13 g hemoglobin/3.92 mg iron). Such unprecedented precise prediction enables reliable pRBC dosing per pharmaceutically active agent, and monitoring iron uptake in patients and individual iron loss in donors. The model is implemented in a free open source web application to facilitate clinical application.

Techniques used for the screening of hemoglobin levels in blood donors: current insights and future directions

Blood donor hemoglobin (Hb) estimation is an important donation test that is performed prior to blood donation. It serves the dual purpose of protecting the donors' health against anemia and ensuring good quality of blood components, which has an implication on recipients' health. Diverse cutoff criteria have been defined world over depending on population characteristics; however, no testing methodology and sample requirement have been specified for Hb screening. Besides the technique, there are several physiological and methodological factors that affect accuracy and reliability of Hb estimation. These include the anatomical source of blood sample, posture of the donor, timing of sample and several other biological factors. Qualitative copper sulfate gravimetric method has been the archaic time-tested method that is still used in resource-constrained settings. Portable hemoglobinometers are modern quantitative devices that have been further modified to reagent-free cuvettes. Furthermore, noninvasive spectrophotometry was introduced, mitigating pain to blood donor and eliminating risk of infection. Notwithstanding a tremendous evolution in terms of ease of operation, accuracy, mobility, rapidity and cost, a component of inherent variability persists, which may partly be attributed to pre-analytical variables. Hence, blood centers should pay due attention to validation of test methodology, competency of operating staff and regular proficiency testing of the outputs. In this article, we have reviewed various regulatory guidelines, described the variables that affect the measurements and compared the validated technologies for Hb screening of blood donors along with enumeration of their merits and limitations.

Predonation finger lancet punctures: a potential risk factor for interdonor pathogen transmission in the blood donor clinic

BACKGROUND AND OBJECTIVES

Point-of-care testing using capillary blood from a finger prick is widely used for predonation haemoglobin testing of blood donors. It is common practice to cover the finger prick with a cotton swab and to instruct the donor to press for few minutes. The finger prick can cause blood contamination of surfaces in contact with the lanced finger, especially door handles, risking infectious disease transmission, particularly if another person touching the contaminated door handle also has a punctured fingertip.

MATERIALS AND METHODS

First, we investigated contamination by blood (benzidine assay) of the door handles of our blood donor clinic, taking 175 samples 3 h after opening of the donation centre (baseline). We then introduced band-aids to cover the finger prick and started an information campaign using educational flyers to sensitize blood donors and staff to this problem (period-1). Thereafter, the staff was instructed to use the non-dominant hand for blood sampling and mandated to replace any discarded band-aids immediately (period-2).

RESULTS

At baseline, 82% of the nurse room door handles showed contamination with blood. This decreased somewhat (10-40%) after period-1, but only after immediate mandatory band-aid replacement on any donor finger without a band-aid (period-2), no further blood contaminations were detected.

CONCLUSION

Blood contamination of shared surfaces can occur after finger prick for capillary blood sampling. Application of a band-aid and use of the non-dominant hand for fingertip incision are easy to apply and effective in reducing this iatrogenic health hazard.

A non-invasive strategy for haemoglobin screening of blood donors

INTRODUCTION

Assessing blood-donor haemoglobin (Hb) is a worldwide screening requirement against inappropriate donation. The pre-donation Hb (which should be at least 12.5 g/dL in women and 13.5 g/dL in men) is usually determined in capillary blood from a finger prick, using a spectrophotometer which reveals the absorbance of blood haemolysed in a microcuvette. New non-invasive methods of measuring Hb are now available.

MATERIALS AND METHODS

In the first semester of 3 consecutive years three different strategies were employed to screen donors for anaemia at the moment of donation. In 2011 all whole-blood donors underwent the finger-prick method using azide-methaemoglobin: the test's negative predictive value (NPV) was determined by comparison with the sub-threshold Hb values ascertained by haemocytometry of test-tube blood drawn at the start of the donation. In 2012 the donor evaluation was based on NBM 200 occlusion spectrophotometry. The same approach was kept in 2013, but a haemocytometry test was added on a pre-donation venous sample drawn from donors who, though fit to donate, had previous critical Hb values in their clinical records.

RESULTS

In 2011, the NPV (in 3,856 donors) was 86% for women and 95% for men; in 2012 (3,966 donors), the values were 85% and 95%, respectively, and in 2013 (3,995 donors) they were 91% and 97%, respectively. Fisher's test for contingency tables revealed no statistically significant differences between 2011 and 2012, but the 2013 results were a significant improvement.

DISCUSSION

Measuring Hb by finger prick is not wholly satisfactory since, above all in women, the result of this screening may subsequently be belied by the haemocytometry finding of an unacceptable Hb value. Using a non-invasive method does not diminish the selective efficiency. In women, in particular, adding a haemocytometric test on a venous sample significantly improves donor selection and avoids the risk of inappropriate donation or blood-letting.

Donor cycle and donor segmentation: new tools for improving blood donor management

BACKGROUND AND OBJECTIVES

An adequate donor population is of key importance for the entire blood transfusion chain. For good donor management, a detailed overview of the donor database is therefore imperative. This study offers a new description of the donor cycle related to the donor management process. It also presents the outcomes of a European Project, Donor Management IN Europe (DOMAINE), regarding the segmentation of the donor population into donor types.

MATERIALS AND METHODS

Blood establishments (BEs) from 18 European countries, the Thalassaemia International Federation and a representative from the South-Eastern Europe Health Network joined forces in DOMAINE. A questionnaire assessed blood donor management practices and the composition of the donor population using the newly proposed DOMAINE donor segmentation. 48 BEs in 34 European countries were invited to participate.

RESULTS

The response rate was high (88%). However, only 14 BEs could deliver data on the composition of their donor population. The data showed large variations and major imbalances in the donor population. In 79% of the countries, inactive donors formed the dominant donor type. Only in 21%, regular donors were the largest subgroup, and in 29%, the proportion of first-time donors was higher than the proportion of regular donors.

CONCLUSION

Good donor management depends on a thorough insight into the flow of donors through their donor career. Segmentation of the donor database is an essential tool to understand the influx and efflux of donors. The DOMAINE donor segmentation helps BEs in understanding their donor database and to adapt their donor recruitment and retention practices accordingly. Ways to use this new tool are proposed.

The difference between fingerstick and venous hemoglobin and hematocrit varies by sex and iron stores

BACKGROUND

Fingerstick blood samples are used to estimate donor venous hemoglobin (Hb).

STUDY DESIGN AND METHODS

Fingerstick Hb or hematocrit (Hct) was determined routinely for 2425 selected donors at six blood centers, along with venous Hb. Using sex and measures of iron status including absent iron stores (AIS; ferritin < 12 ng/mL), linear regression models were developed to predict venous Hb from fingerstick.

RESULTS

Across all subjects, fingerstick Hb was higher than venous Hb in the higher part of the clinical range, but lower in the lower part of the range. The relationship varied by sex and iron status. Across centers, a female donor had on average a venous Hb result 0.5 to 0.8 g/dL lower than a male donor with the same fingerstick Hb and iron status. Similarly, a donor with AIS had on average a venous Hb result 0.3 to 1.1 g/dL lower than an iron-replete donor with the same fingerstick value and sex. An iron-replete male donor with a fingerstick result at the cutoff (Hb 12.5 g/dL) had an acceptable expected venous Hb (12.8 to 13.8 g/dL). A female donor with AIS with a fingerstick result at the cutoff had an expected venous Hb below 12.5 g/dL (11.7 to 12.4 g/dL). Of females with AIS, 40.2% donated blood when their venous Hb was less than 12.5 g/dL.

CONCLUSIONS

Fingerstick is considered a useful estimator of venous Hb. However, in some donor groups, particularly female donors with AIS, fingerstick overestimates venous Hb at the donation cutoff. This significant limitation should be considered in setting donor fingerstick Hb or Hct requirements.

Evaluation of four rapid methods for hemoglobin screening of whole blood donors in mobile collection settings

INTRODUCTION

Predonation hemoglobin measurement is a problematic requirement in mobile donation settings, where accurate determination of venous hemoglobin by hematology analyzers is not available.

OBJECTIVE

We have evaluated hemoglobin screening in prospective donors by the semiquantitative copper sulphate test and by capillary blood samples analyzed by three portable photometers, HemoCue, STAT-Site MHgb, and the CompoLab HB system.

METHODS

Capillary blood samples were obtained from 380 donors and tested by the copper sulphate test and by at least one of the named portable photometers. Predonation venous hemoglobin was also determined in all donors using a Coulter Max-M analyzer.

RESULTS

The three photometers provided acceptable reproducibility (CV below 5%), and displayed a significant correlation between the capillary blood samples and the venous hemoglobin (R2 0.5-0.8). HemoCue showed the best agreement with venous hemoglobin determination, followed by STAT-Site MHgb, and the CompoLab HB system. The copper sulphate test provided the highest rate of donors acceptance (83%) despite unacceptable hemoglobin levels, and the lowest rate for donor deferral (1%) despite acceptable hemoglobin levels. The percentage of donors correctly categorized for blood donation by the portable hemoglobinometers was 85%, 82%, and 76% for CompoLab HB system, HemoCue and STAT-Site, respectively.

CONCLUSION

Our data suggest that hemoglobin determination remains a conflictive issue in donor selection in the mobile setting. Without appropriate performance control, capillary hemoglobin screening by either the copper sulphate method or by the novel portable hemoglobinometers could be inaccurate, thus potentially affecting both donor safety and the blood supply.

Selection of whole-blood donors for hemoglobin testing by use of historical hemoglobin values

BACKGROUND

Usually, a predonation hemoglobin (Hb) measurement must precede blood donation. Hb values of a donor's previous donation might be used for selecting a subgroup in which predonation Hb measurements are unnecessary.

STUDY DESIGN AND METHODS

Only donors with historical Hb values below 129 or 139 g per L for female and male donors, respectively, underwent venous Hb measurement before phlebotomy with an automated hematology analyzer. All other donor phlebotomies were collected without initial Hb testing. Hb values from diversion samples from 81,913 consecutive donors between May 2003 and November 2005 were subsequently analyzed as representing their present values. Donors were grouped according to interdonation intervals of less than 6, 6 to 11, 12 to 23, and 24 months or more.

RESULTS

The arithmetic mean deviation between historical and present Hb values was between -0.3 and +1.8 g per L for each group (mean deviation, 5.2-6.7 g/L). Not testing selected donors spared 77.7 percent from a prephlebotomy Hb measurement and showed a specificity of 29 percent. Sensitivities for detection of donors below Hb limits (between 56% and 67% for the different subgroups) and donors with Hb values below 110 g per L (82%-88%) were at least comparable to capillary Hb screening. A total of 4.8 percent of donors were phlebotomized with values below 125 and 135 g per L, whereas only 0.016 percent of donors were bled despite Hb levels below 110 g per L.

CONCLUSION

Selecting donors for a current Hb measurement based upon their last whole-blood predonation Hb value is a useful method, even after prolonged interdonation intervals.

Utility of point-of-care haemoglobin measurement in the HemoCue-B haemoglobin for the initial diagnosis of anaemia

Measurement of haemoglobin (Hb) concentration provides a reliable indication of the presence and severity of anaemia. However, other laboratory parameters are usually requested as well, leading to an increase in socio-sanitary costs. Accordingly, this study was undertaken to ascertain the reliability of point-of-care Hb determination with the portable photometer HemoCue-B haemoglobin (HBH) and to evaluate its utility for the initial diagnosis of anaemia. Hb was measured (x3) in 20 venous blood samples diluted with saline (v/v; 1 : 0, 2 : 1, 1 : 1, 2 : 1 and 3 : 1) to obtain a wide range of Hb and in venous and capillary blood samples from 247 primary health care patients. All HBH results were compared with those yielded by the reference cell counter Pentra 120 Retic (ABX). In diluted samples, Hb values obtained with either method were not significantly different (ABX-HBH, -0.01 +/- 0.32 g/dl; 95% CI, -0.04 to 0.028 g/dl) and showed an excellent Pearson's coefficient of correlation (r = 0.992; P < 0.01). HBH provides accurate values if at least 4 mul of blood is loaded into the cuvette. There were no significant differences between Hb measured in venous (v) and capillary (c) blood samples in primary care patients. Eighteen anaemic patients were detected by ABX measurements (7.3%; 15 female/3 male), 18 by HBHv (specificity, 100%; sensitivity, 100%) and 25 by HBHc (eight false positives; one false negative; specificity, 94.4%; sensitivity, 96.5%). Compared with ABX, HBH provides accurate and precise measurements for a wide range of Hb and its use in primary health care seems to be a good method for the initial diagnosis of anaemia.