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The new noninvasive occlusion spectroscopy hemoglobin measurement method: a reliable and easy anemia screening test for blood donors

Jul. 14, 2012

The new noninvasive occlusion spectroscopy hemoglobin measurement method: a reliable and easy anemia screening test for blood donors

Márcio Pinto, Maria Lourdes Barjas-Castro, Simone Nascimento, Mônica Almeida Falconi, Roberto Zulli, and Vagner Castro

From the Blood Collection Facility and the Hematology Laboratory, the Transfusion Medicine Laboratory, the Hematology Laboratory, and Statistics, Hematology and Hemotherapy Center, University of Campinas, UNICAMP, Campinas, Brazil.

BACKGROUND: The tests used for anemia screening in blood donors are based on fingerstick samples, leading to discomfort and complaints. The aim of this study was to analyze the feasibility of occlusion spectroscopy method in blood banks and to compare the method with fingerstick hemoglobinometer and hemoglobin (Hb) determination on an automatic blood analyzer.

STUDY DESIGN AND METHODS: The study enrolled 205 consecutive volunteer blood donors. Samples were collected by fingerstick and venous punction to determine Hb level by a Hemocue Hb201+ (Hb-F) and automatic blood analyzer (Hb-V) and compare to the noninvasive Hb determination by occlusion spectroscopy using NBM200 system (Hb-NI). The percentage errors of Hb-F and Hb-NI of all donors as well as stratified by sex, weight, and age levels were compared to Hb-V as reference values using Wilcoxon signed rank test.

RESULTS: The results obtained with Hb-F showed significant errors (p < 0.001) in the general group as well as when stratified by sex, weight, and age groups, above values obtained with Hb-V. Hb-NI showed significant errors only in females (p = 0.026) and weight level of 61 to 70 kg (p = 0.034), below Hb-V values.

CONCLUSIONS: Hb-NI seems to be a good method in terms of precision and feasibility for anemia screening of blood donors as well as being much more comfortable for donors.

Blood donation remains the only source for providing support to patients who require blood transfusion. Nevertheless, frequent blood donation may lead to iron deficiency in blood donors, particularly in females,1 demanding screening tests such as hemoglobin (Hb) or hematocrit (Hct) determination. These tests are performed to prevent collection of blood from a donor with significant anemia, which could have implications upon the health of the donor and the quality of the red blood cell unit.2 Indeed, low Hb or Hct levels (<12.5 g/dL or 38%, respectively) is the most frequent cause of donor deferral in the United States2 and is also a frequent cause in Brazil.3,4 National regulations usually have directions to prevent at-risk donors from donating blood, in which anemia screening tests are demanded.5 The most widely used screening tests are the fingerstick Hb or Hct determination, which do not represent the iron status of donor, but are fast and easily performed. Both tests involve digital needle punction to obtain samples, leading to blood donor discomfort and complaints. Recently, a new method to determine Hb levels has been developed, using the principle of occlusion spectroscopy,6,7 which exempts the donor fingerstickand makes the procedure more comfortable andcould therefore contribute to greater donor retention. There are to date, few data available regarding the use of this method in blood transfusion facilities. The aim of this study was to analyze the feasibility of the use of this new method, as well as to compare Hb levels with fingerstick hemoglobinometer in routine use and with venous Hb determination on automatic blood analyzer.

This study enrolled consecutive volunteer blood donors of both sexes, during August 2011, after informed consent was obtained explaining the need of a venous blood sample in addition to the routine fingerstick sampling defined by national regulation5 and also the application of the device on their finger to perform the Hb measurements using the new method.

Fingerstick sampling and Hb screening test
Blood samples of each donor were obtained by fingerstick for Hb testing using Hemocue Hb201+ (Hb-F; Hemocue AB, Ängelholm, Sweden), according to manufacturer’s directions. This method is routinely used as an anemia screening test in the regional blood center and in mobile units and is performed in approximately 60 seconds.

Venous punction for Hb determination
Ethylenediaminetetraacetic acid–anticoagulated venous blood samples were obtained from donors for Hb determination in a automated hematologic analyzer (CellDyn Ruby, Abbott Laboratories, Abbott Park, IL). Samples were analyzed within 30 minutes after collection, after variables of the analyzer had been checked with commercially available controls (low, high, and normal Hb, Abbott Laboratories). The values obtained in donor sample analysis were used as reference values to compare with the two Hb screening tests.

Noninvasive Hb determination
The noninvasive occlusion spectroscopy Hb determination was performed using a noninvasive Hb measurementsystem (Hb-NI; NBM200, Orsense Ltd., Nez Ziona, Israel). Briefly, a pressure is applied by a ring-shaped multiwave length sensor probe containing a pneumatic cuff that temporarily occludes the blood flow in the base of the finger and generates a strong optical signal, yielding a high signal-to-noise ratio that is wholly blood specific. Analysis of the signal in the wavelength range of 600 to 1500 nm provides the necessary sensitivity for measuring Hb concentration and pulse rate. The test is performed in 90 seconds, according to manufacturer’s instructions.

Statistical analysis
The results of Hb determination by the three methods were tabulated on a data sheet containing donor sex, age, and weight, which could impact the results. Donor age and weight were stratified in levels:18to 25,26to 35,36to 45,and 46 to 65 years and 50 to 60, 61 to 70, 71 to 80, 81 to 90, 91 to 100, and 101 to 128 kg, respectively, to permit comparisons.

The percentage error of Hb levels of results obtained by Hb-F and Hb-NI were calculated using the venous determination with the CellDyn (Hb-V) as a reference value for each donor. The difference of the median of these errors for both Hb-NI and Hb-F was compared to “0” value (no difference to reference) and evaluated by Wilcoxon signed rank test using computer software (R,8 Version 2.13.1, http:// cran.r-project.org/bin/windows/base/). Comparisons were made among data of total group and stratified by age, sex, and weight. Significant differences were defined by p values of less than 0.05.

The results of Hb determination by the three methods are summarized on Table 1. A total of 205 donors with ages of 18 to 65 years (median, 32 years), of which 136 were males and 69 females, were evaluated, with median weight of 78 kg (variation, 52-128 kg). The analysis of the percentage error showed significant differences (p  < 0.001) between Hb-F and Hb-V (reference level) in the total group (Fig. 1), as well as in the stratified results by sex and age (Fig. 2). The median of these errors was higher than the results obtained with Hb-V. When the percentage error between Hb-NI and Hb-Vwere compared, no differences were found in the whole group. However, when stratified data for sex, age, and weight were analyzed, significant differences were observed in percentage errors for females (p = 0.026) and in the weight level 61 to 70 kg (p = 0.034; Fig. 3). In these two situations, the median of the errors was below that of the results obtained with Hb-V.

The determination of Hb levels in blood donors is usually performed before donation and samples are obtained by fingerstick, which is painful and leads to frequent donor complaints. This study obtained results indicating that the Hb-NI is a feasible and noninvasive method (exempts fingerstick, needle/lancets manipulation) to screen donors. Indeed, it is safe, easy to perform, and quick and does not require extremely specialized technicians. It may also be used in mobile units due to its portability and may be used with power supply or batteries (which allows approximately 100 tests per battery). An issue that must be taken into account is the higher cost per test of Hb-NI (R$2.20 or approximately US$1.13 in local market) compared to the Hb-F (R$0.94 or around US$0.50). The greater use in different services and situations could make evident certain limitations of the equipment that were not detected initially in this study.
The results obtained suggest that Hb-NI is even more precise than the routine accepted Hb-F in use, preventing donation by anemic donors, since the median of percentage error observed was below that observed with the reference method—Hb-V (Fig. 3). On the other hand, this could lead to unnecessary donor deferral due to “false” low Hb, particularly among females, but the consequences of this effect seem to be of lower risk to donors than allowing donation by anemic individuals.
Hb-F showed the median of these errors above the results obtained with Hb-V (Fig. 2), suggesting that this method may permit donation from blood donors with low Hb. It is important to note that venous Hb is slightly lower than in capillary blood, which could in part explain the results obtained in this study.9,10
In conclusion, Hb-NI seems to be a good method in terms of precision and feasibility for anemia screening of blood donors as well as being much more comfortable for donors.

Authors have no conflicts of interest to disclosure.

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