Hemoglobin Estimation Test Manually (by Drapkin’s method) or hemiglobinocyanide method-The method only


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Hemoglobin Estimation Test Manually by Drapkin’s method (i.e. Hemoglobinocyanide method)- The Method only

We will talk about the technique only and we will talk about result interpretations in another sections

Introduction

1) Measuring units:

==> Hemoglobin values are expressed in grams per liter (g/l) or grams per deciliter (g/dl)

==> To convert from g/l to g/dl divide by 10 (i.e. 10 g/l = 1 g/dl) because 1 dl = 100 ml and 1 Liter = 1000 ml thus 1 liter = 10 dl, so, to convert from liter to dl you should multiply by 10 and because L and dl is in the denominator, we said that you should divide by 10 to convert from ((g/l)) to ((g/dl))

==> g/dl may be written g/100ml in some books because (1 dl = 100 ml)

==> Grams/litre is the recommended way of expressing the mass concentration of hemoglobin. Some countries however continue to express hemoglobin in g/dl and most visual comparative techniques use g/dl.

==> Some labs and kits use mmol/l, but i believe that it is not accurate because the mmol depends on the molecular weight of hemoglobin and this is varies according to the type of hemoglobin.

2) Techniques for measuring hemoglobin and assessing anemia:

hemoglobin is measured by:

  • Photometric techniques or

  • Visual comparative Techniques

A) Photometric techniques



==> In photometric techniques the absorbance of haemoglobin in a blood sample is measured electronically using a filter colorimeter or a direct read-out haemoglobin meter.

==> It can be classified into:

Techniques include dilution techniques, and non dilution techniques which do not require prior dilution of the blood.

 1) DILUTION TECHNIQUES 

“In which blood is measured into a measured volume of diluting fluid”

These include:

===> Hemiglobinocyanide (cyanmethemoglobin)

==> It is a technique using a filter colorimeter or direct read-out meter.

==> It is the recommended technique because stable hemiglobincyanide (HiCN) standards are available to calibrate instruments.

==> It has however, several disadvantages when used in tropical countries.

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===> Alkaline haematin D-575

==> It is a technique using a filter colorimeter or direct read-out meter.

==> It is as accurate as the hemiglobincyanide technique but less expensive and uses a diluting reagent that does not contain toxic potassium cyanide.

==> A crystalline compound, chlorohaemin is used to calibrate the method (requires preparation in the Central or Regional Laboratory).

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===> Using a direct read-out meter

 

300209_10150384998071071_51056136070_10531434_1901444067_n==> Such as the Developing Health Technology (DHT) Hemoglobinometer which is a hemoglobin meter with specifications and technique suitable for use in district laboratories in tropical countries.

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 2) NON-DILUTION TECHNIQUES 

which do not require prior dilution of the blood where Blood is collected directly into a specially designed single-use microcuvette or other sampling device which is internally coated with reagent to lyse the blood and convert hemoglobin to a form which can be read in a direct read-out meter

While the cost of direct read-out meters for use with non-dilution systems is becoming less, the cost of the sampling devices remains high compared with most dilution systems, particularly the DHT Hemoglobin system.

These include:

HemoCue systemHemoCue system

==> This non-dilution system is becoming more widely used in tropical countries because of the lower cost of the new hemoglobin meter, its accuracy, and simplicity of use.

==> It is particularly useful when a dilution technique cannot be used, e.g. in a clinic with nursing staff performing hemoglobin tests.

B) Visual comparative technique

When it is not possible to measure hemoglobin accurately using a photometric technique, e.g. in a health center or antenatal unit, a visual comparative technique such as the Hemoglobin Colour Scale, can help to detect anemia and assess its severity.

Other hemoglobin test methods

See the principle and reagents in page 2

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