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What is a Haemoglobin test?

Red blood cells (RBCs) contain a protein haemoglobin, which imparts a red colour to blood and transports oxygen. Haemoglobin test is a laboratory test that measures the concentration of haemoglobin in blood cells. This test is often done as part of complete blood count and haematocrit tests. Hence, measuring haemoglobin concentration helps estimate the oxygen-carrying capacity of blood. Lower than normal values of haemoglobin suggest an anaemic condition. However, in rural areas or during blood donation, it is particularly easier to use a portable haemoglobin measurement device. There are many methods to determine haemoglobin concentration in blood. Nowadays, an automated haematology analyser is commonly employed in clinical pathology laboratories. The World Health Organisation (WHO) also recommends a haemoglobin colour scale test; however, it does not provide accurate results.

  1. Why is a Haemoglobin test performed?
  2. How do you prepare for a Haemoglobin test?
  3. How is a Haemoglobin test performed?
  4. What do Haemoglobin test results indicate?

When RBCs are not able to meet physiological needs due to low oxygen-carrying capacity, the condition is called anaemia. It is characterised by less than normal concentrations of haemoglobin in blood and is diagnosed primarily using a haemoglobin test. Haemoglobin test is most commonly recommended in malnourished children and pregnant women. The following symptoms may suggest the need for haemoglobin test:

  • Pallor
  • Stomatitis
  • Glossitis
  • Spoon-shaped nails
  • Premature greying
  • Muscle weakness
  • Headache
  • Drowsiness
  • Peripheral neuropathy
  • Loss of blood
  • Existing disease conditions, such as thalassemia, bone marrow hypoplasia, splenomegaly and some inflammatory conditions
  • Pregnancy

Haemoglobin test is very simple and inexpensive. It does not need any special preparation. No fasting is required unless some other tests are advised along with it. This test can be performed in less than 5 minutes in a pathology lab or an outpatient facility.

A skilled laboratory technician collects a blood sample by inserting a needle into a vein of a hand or arm in case of adults; a finger stick may be used in small children, whereas a heel stick is used in newborns. Before withdrawing blood, the technician may ask you to tightly close your fist and an elastic band is applied on the upper arm to ease the flow of blood. Blood is collected into a sterile tube or vial and sent for analysis. For blood donation, donors can undergo a new method of haemoglobin testing in which the donor’s finger is pricked, and a blood drop is placed into a vial containing copper sulphate solution; if the drop of blood sinks, the person can donate blood.

Another method uses a Hemo Cue machine to do a similar analysis. One may experience mild pain or discomfort at the site of needle insertion. There are no significant side effects associated with this test.

Normal results: Normal haemoglobin levels vary based on gender and pregnancy status of women. The normal range is as follows:

  • Females: 12.1-15.1 grams/deciliter (g/dL)
  • Males: 13.8-17.2 g/dL;
  • Children: 11-16 g/dL; and
  • Pregnant females: 11-15.1 g/dL.

Normal results of a haemoglobin test suggest an absence of anaemia and other complications associated with it.

Abnormal results: Lower than normal values of haemoglobin normally suggest a form of anaemia. This can be categorised as mild, moderate or severe depending on the exact value. Low levels of haemoglobin could be due to the following conditions:

High haemoglobin levels are normal in new-born babies but abnormal in adults. Abnormally high values may signify:

  • Polycythaemia vera, a condition in which bone marrow produces a lot of RBCs usually due to a genetic mutation
  • Congenital heart disease
  • Lung diseases, such as chronic obstructive pulmonary disease (COPD) and pulmonary fibrosis
  • Kidney disease

Abnormal haemoglobin levels need to be correlated with other clinical findings, and obtaining a thorough patient history is equally important to know pre-existing diseases.

A haemoglobin test is mostly done as part of collective blood count test, and hence the other parameters in the test are useful in detecting the exact disease condition. Determination of folate and vitamin B12 levels can also help determine the underlying cause of the anaemic condition when haemoglobin levels appear to be low. A blood smear test to evaluate the morphology of RBCs can also be a supportive test. Thus, in conclusion, a haemoglobin test is an easy, quick and inexpensive method to measure haemoglobin levels in blood.

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational perspective and is in no way a substitute for medical advice from a qualified doctor.

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References

  1. Khaled SA, Seifeldei GS. Splenomegaly in Patients With Sideropenic Anemias: Clinical and Hematologic Significance. J Hematol. 2016;5(3): 83-93.
  2. Tortora G and Derrickson B, Principles of anatomy and physiology, 14th Ed Wiley. Chapter 19. The cardiovascular system: the blood pp 662-668.
  3. Drew P. Oxford handbook of clinical and laboratory investigation, 4th Ed 2018. Oxford University Press, Chapter 1 Symptoms and signs pp 10-11.
  4. National Health Portal India. Centre for Health Informatics. National Institute of Health and Family Welfare: Ministry of Health and Family Welfare (MoHFW), Government of India; Iron Deficiency Anemia
  5. National Health Service. Blood and transplant [internet]. UK; New haemoglobin test
  6. Yang X, Piety NZ , Vignes SM, Benten MS, Kanter J, Shevkoplyas SS. Simple paper-based test for measuring blood hemoglobin concentration in resource-limited settings.. Clin chem. 2013;59(10). doi:10.1373/clinchem.2013.204701.
  7. Parker M, Han Z, Abu-Haydar E, Matsiko E, Iyakaremye D, Tuyisenge L, et al. An evaluation of hemoglobin measurement tools and their accuracy and reliability when screening for child anemia in Rwanda: A randomized study. PLoS ONE. 2018;13(1): e0187663. https://doi.org/ 10.1371/journal.pone.0187663