TABLE 3.

Summary of various method and analyzer characteristics used for hemoglobin measurement

Method/analyzer	Setting	Method principle	Blood volume (μL)	Cost/test CM as referencea	Calibration reagents
Cyanmethemoglobin method (CM)a	Clinical laboratory	Hb is converted into methemoglobin, and to cyanmethemoglobin by adding potassium cyanide and ferricyanide. Absorbance is then measured at 540 nm using a photoelectric colorimeter against a standard quality control solution.	10–200	1 US$	Drabkin’s reagent
Automated hematology analyzers	Clinical laboratory	Hb is converted into methemoglobin, cyanmethemoglobin, or other Hb derivatives, and measured at the wavelength that is more specific for the Hb derivative. They can also identify and measure physical characteristics of the red blood cells and other blood cells.	200	5–10× CM	Quality control material specific to the analyzer
Point-of-care photometric analyzers (e.g., HemoCue, Hemo-Control, Hb-Quick, DiaSpect, URIT, and TrueHb)	Clinical laboratory and field settings	For the Hb-201+, Hemo-Control, and Hb-Quick, Hb is converted to methemoglobin by sodium nitrate from the ferrous to ferric state to form azide-methemoglobin, where the Hb concentration is then detected at 570 and 880 nm and read using a photoelectric colorimeter. For the Hb-301, the Hb concentration is simply determined by the photoelectric colorimeter.	10	2–4× CM	Not required for Hb-201+, Hb-301, Hemo-Control, DiaSpect, TrueHb, and URIT, but HemoTrol and EuroTrol have liquid controls
Paper- or color-based analytical devices (e.g., μPADs and color-based filter test)	Clinical laboratory chromatography paper with a wax finish that is heated at 150°C for 3 min	Blood samples are diluted with Drabkin’s reagent and then incubated for 10 min. A 20 μL sample of blood is then placed onto the paper-based analytical device, and the Hb concentration is then read using a portable flatbed scanner after the sample dries.	20	2× CM	Drabkin’s reagent
WHO color scale	Clinical laboratory and field settings	Contains six shades of red (i.e., lighter to darker, corresponding to an Hb concentration of 40, 60, 80, 100, 120, and 140 g/L) that are mounted onto strips. A drop of blood is placed onto a moveable piece of filter and compared to the shades of red on the color scale.	30	<CM	None
Color-based analytical devices	Clinical laboratory and field settings	Uses small round tube with a cap that holds the solution, which mixes with the blood sample that enters the device via capillary action. The sample is then compared to a color chart with a range of colors.	5	=CM	Drabkin’s reagent
Sahli method	Field settings	Hydrochloric acid converts hemoglobin to acid hematin, which is then diluted until the color of the solution matches that of the comparator block.	20	<CM	Hydrochloric acid
Copper sulfate method	Clinical laboratory	Hb concentration based on the estimation of specific gravity from a blood sample. Specific gravity value of 1.053 corresponds to an Hb concentration of 125 g/L.	10	=CM	Fresh anticoagulated blood samples
Noninvasive analyzers (e.g., Masimo)b	Clinical laboratory	CO-oximeter measures the oxygen saturation, pulse rate, perfusion index, and total Hb by detecting the levels of oxygen and carbon monoxide bound to Hb in the individual. This is done by placing a probe on the finger.	–	2–5× CM	–

Note: Adapted from Ref. 9.

Abbreviation: Hb, hemoglobin.

^aCyanmethemoglobin method is used as the reference for cost comparisons.

^bDoes not require a blood sample.