A review of new methods of hemoglobin testing
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Mirmaghsoud Tabatabae Asl,1 Hassan Hajghassem,2,* Elahe Asgari,3 Mahsa Kalantar,4 Amir Mohamadsharifi,5 Erfan Safaie,6
1. University of Tehran
2. University of Tehran
3. Sahand university of technology
4. University of Tehran
5. University of Tehran
6. University of Tehran
- Introduction: Measuring hemoglobin levels in medicine and health is very important for diagnosing and preventing diseases like anemia and blood concentration. Rapid methods and portable devices are vital in emergencies and poor areas with inadequate health facilities. Challenges such as accuracy, measurable interval, maintenance conditions and cost of measuring equipment and devices, environmental compatibility, and reproducibility of hemoglobin measurement method have always been raised. Therefore, a study has been performed on hemoglobin measurement methods and measurement methods adopting microfluidic technology. Also, some examples of microfluidic systems used in hemoglobin measurement are described.
- Methods: Reagent-based and reagent-free approaches are two general hemoglobin concentration (Hb) measurement methods on microfluidic systems. The reagent-based methods are Drakbin(HiCN), azide methemoglobin, and sodium lauryl sulfate(SLS). They use reagents to turn the hemoglobin into a chemical product with an absorbance maximum at a specific wavelength. Then the Hb is measured by Beer-Lambert’s law. The Drakbin method employs the solution of potassium cyanide (KCN) and potassium ferricyanide (K3Fe(CN)6) to turn hemoglobin and its derivatives into cyanomethemoglobin(HiCN). HiCN is a stable colored product, which in solution has an absorbance maximum at 540 nm and obeys Beer-Lambert’s law. It was implemented on a microfluidic blood cuvette to measure Hb by Kim et al. The microfluidic blood cuvette was filled with blood samples by capillary force, and hemoglobin levels in the blood were determined by measuring the absorbance of a perpendicular beam incidence at the wavelength of 540 nm. The azide methemoglobin method takes a reagent combination of sodium nitrate, sodium azide, and sodium deoxycholate that turns hemoglobin into azide methemoglobin with an absorbance maximum at 580 nm. Based on the azide methemoglobin method, Yao et al. have developed a portable Hb determinator, utilizing the disposable microcuvette containing reagent, which could be used for performing the quick test of undiluted and unhemolyzed whole blood within 30 seconds. Correspondingly the SLS method uses the SLS reagent to turn hemoglobin into SLS-methemoglobin with an absorbance at 540nm. Grumann et al. have developed a novel concept for optical beam guidance by total internal reflection (TIR) at V-grooves as retroreflectors which are monolithically integrated on a microfluidic “lab-on-a-disk” using the SLS method measurement. The optical path length through a measurement chamber and the sensitivity of colorimetric assays are enhanced compared to direct beam incidence. Reagent-free is a patented method that Hemoglobin fractions are measured from absorbance wavelengths between 400 and 800 nm. The DiaSpect System is a newly developed reagent-free technology for measuring Hb in unaltered blood in a special cuvette that serves as the sampling device.
- Results: The Drakbin method is the international standard and consists of inexpensive reagents. Still, the reagents are hazardous because of cyanide presence limiting its use outside the laboratory. Microfluidic blood cuvettes were designed and fabricated to measure Hb by Kim et al. they found that 105 um deep microchannels showed linearity 99.2% compared to 94.5% for 35um deep microchannels. Moreover, microchannel depth must be >100 μm to eliminate blood aggregation. The hemoglobin measuring system developed by Yao et al. is based on the azide methemoglobin method to measure the self-developed reagent microcuvette, which can measure Hb of whole blood within 30 seconds, with the accuracy of 0.1g/dl. Grumann et al. introduced a chip-based, non-invasive method for colorimetric assays with a laser diode and detector. The method is based on the total internal reflection (TIR) at monolithically integrated beam-guidance structured in a polymer substrate. Outstanding features are a high degree of linearity (R^2 = 0.993) between the optical signal and the Hb together with reproducibility of CV= 2.9 % and a time-to-result of 100 seconds. The DiaSpect is a reagent-free hemoglobin measurement device that displays the results within 5 seconds as g/dl in a measurement range of 0 to 25.5 g/dL, And accuracy of 0.3 g/dL for 0 to 20 g/dL and 0.7 g/dL for more than 20 g/dL.
- Conclusion: Reagent-free methods for shelf life and environmental compatibility are the priority. However, it has an accuracy of 0.3 g/dl, and they use high technology devices. Contrarily, the reagent-based methods are more accurate than 0.1 g/dl, and they need low-cost equipment. The HiCN method contains hazardous materials, and the Azide methemoglobin method consists of explosives. Nevertheless, the SLS method employs eco-friendly materials.
- Keywords: microfluidics, hemoglobin measurement
