Very anemic donors may pass copper sulfate screening tests

Evidence-based criteria for the care and selection of blood donors, with some comments on the relationship to blood supply, and emphasis on the management of donation-induced iron depletion

Blood Services, which, in the UK, spend over 0.5% of the NHS budget, are generally subject to quality, regulatory, economic and political authority. As only persons in good health should give blood, Services have refined donor selection criteria and aim to base them on evidence; but they also have to balance the number of donations collected with product demand. Applying selection criteria inevitably leads to deferrals, which donors experience very negatively. Compared with successful donors, even temporary deferrals reduce return rates significantly, especially of first attenders. In order to encourage donor return and sustain supplies, selection criteria should be optimal. However, a major tool for managing patients--evidence from randomized controlled trials (RCTs)--cannot apply to donor selection, so criteria have to be defined by alternatives, such as clinical studies, epidemiology and even what experts deem to be pathophysiologically feasible. The recommended volume of blood taken from each donor at each attendance (450 mL, which was based on old studies) was increased because of greater processing losses (buffy-coat derived platelets, leucofiltration etc.). Although faint rates and donation-induced iron depletion are reduced by lowering bleeding volume and bleeding less frequently, other optimizing strategies including iron supplementation have been trialled and could be enhanced by more RCTs. Better but more complex indicators of donor iron status than one-off Hb thresholds are possible. Regulators and decision-makers must encourage more studies. This review does not consider aphaeresis donors of blood components other than red cells in detail, or the prevention of transfusion-transmitted infections.

Evaluation of hemoglobin of blood donors deferred by the copper sulphate method for hemoglobin estimation

INTRODUCTION

The copper sulphate (CuSO4) specific gravity test for Hb screening tends to give inappropriate failures. This prompted us to compare it with alternate screening methods.

AIM

To study the impact of inaccuracy of CuSO4 method on donor deferral.

METHODS

Capillary and venous blood samples of 400 potential blood donors failing the primary Hb screening using appropriately standardized CuSO4 test (specific gravity 1.053) were tested by Hemocue photometer, the Hb colour scale, Cyanmethemoglobin method as well as the automated hematology analyser, which was considered as the standard reference method.

RESULTS

One hundred and sixteen donors (29%) who failed the CuSO4 test had true Hb levels >12.5 g/dl. The Hb levels of 131 (32.8%) deferred donors were between 12 and 12.5 g/dl. The sensitivity of Hemocue, Hb colour scale and Cyanmethemoglobin was 99%, 97% and 96% and their specificity was 45%, 93% and 46%, respectively. The positive predictive values (PPV) of Hemocue and Cyanmethemoglobin methods were low (43% and 44%, respectively) but their negative predictive values (NPV) were high (99%, and 97%, respectively). The Hb colour scale had an overall best performance with a PPV of 96% and NPV of 95%.

CONCLUSION

The Hemoglobin colour scale which is inexpensive, convenient for field testing and has the overall best performance, is the most suitable for donor Hb screening. Since its readability is 12 g/dl, lowering the donor Hb threshold to 12 g/dl should be actively considered.

Statistical analysis of inappropriate results from current Hb screening methods for blood donors

BACKGROUND

The objective was to apply statistical analysis to the false passes and fails that occur with the primary and secondary Hb-screening methods used at blood-donor sessions.

STUDY DESIGN AND METHODS

Venous samples from 1513 potential donors who had undergone primary CuSO4 screening using capillary blood (Hb cut-offs: women, 125 g/L; men, 135 g/L) were tested at the session by a secondary method (HemoCue; cut-offs: women, 120 g/L; men, 130 g/L) and again at the base laboratory using another system (Beckman Coulter General S system), which generated the "true" Hb value.

RESULTS

False-pass and -fail rates for women and men, respectively, were 11.2 and 6.3 percent (women) and 5.2 and 1.8 percent (men) for CuSO4; 1.9 and 3.7 percent (women) and 1.5 and 0.4 percent (men) for HemoCue; and 2.7 and 2.4 percent (women) and 1.8 and 0.2 percent (men) for a combined procedure that mimicked current practice of only testing CuSO4 fails by HemoCue.

CONCLUSION

CuSO4 Hb screening gives large numbers of false passes, particularly in women. Using venous samples, the majority correctly pass at the lower HemoCue cut-offs. The current dual-testing policy appears convenient for donor sessions, but because small percentages of false passes and fails represent large numbers of donors, every effort should be made to improve the accuracy of Hb screening.

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

BACKGROUND

Safe blood donation depends upon reliable predonation Hct screening. Earstick (ES) capillary samples are frequently used, but they may not be accurate.

STUDY DESIGN AND METHODS

Predonation ES and fingerstick (FS) and postdonation venous Hct results were compared in 1960 whole-blood and 210 apheresis donors. The validity of using postdonation venous samples to evaluate predonation ES and FS Hct was assessed in 20 whole-blood donors. The impact of Hct screening method on donor Hct deferrals was examined during periods when either ES or FS sampling was used exclusively.

RESULTS

All donors were eligible to donate on the basis of a predonation capillary Hct of > or = 38 percent. In venous samples obtained immediately after donation, 36 percent of whole-blood donors had a Hct <38 percent. With correction for a decrease of approximately 2 Hct units during donation, 20 percent of these donors had a predonation Hct <38 percent. The lowest venous Hct was 23.1 percent. FS samples showed better correlation with venous Hct. Hct discrepancies were similar for apheresis donors. Hct deferrals were significantly higher with FS sampling, especially among women.

CONCLUSION

Hct determinations from ES samples overestimate venous Hct. Fingerstick samples are more sensitive in detecting anemia. The accuracy of predonation Hct sampling has implications for donor safety, eligibility, and deferral rates.

A study of the iron and HFE status of blood donors, including a group who failed the initial screen for anaemia

A complete data set (age, weight, diet and recent donation history; venous blood cell count, serum ferritin and soluble transferrin receptor concentrations and transferrin saturation; HFE genotype) was obtained from 113 male and 122 female blood donors. Progressive iron depletion and deficiency - most apparent from serum concentrations of soluble transferrin receptor divided by the logarithm of ferritin concentrations (the TfR-F index) - developed in men donating up to six times in 2 years, although the serum ferritin alone was also informative; however, no prediction could be made for those iron-depleted individuals who will develop iron deficiency after donation. Iron stores in the groups of donors with 'low-normal' haemoglobin (Hb) concentrations were indistinguishable from those in donors with higher Hb values, whereas donors failing the anaemia screen had reduced stores. This supports the UK policy of accepting donations from people whose Hb concentration is up to 0. 5 g/dl below the recommended European threshold. Women eating red meat once a week sustained higher ferritin concentrations, and the iron status of first-time women donors resembled that of men donating twice each year. Homozygosity for either HFE variant allowed greater iron retention in the face of regular donation, but among heterozygotes the findings were inconclusive.