29 August 2021
WHO recommendation on the method for diagnosing anaemia in pregnancy
Full blood count testing is the recommended method for diagnosing anaemia during pregnancy. In settings where full blood count testing is not available, onsite haemoglobin testing with a haemoglobinometer is recommended over the use of the haemoglobin colour scale as the method for diagnosing anaemia in pregnancy.
First published: December 2016
Updated: No update planned
Assessed as up-to-date: December 2016
Defined as a blood haemoglobin (Hb) concentration below 110 g/L, anaemia is the world’s second leading cause of disability, and one of the most serious global public health problems, with the global prevalence of anaemia among pregnant women at about 38% (1).
Clinical assessment (inspection of the conjunctiva for pallor) is a common method of detecting anaemia but has been shown to be quite inaccurate. In HICs, performing a full blood count, which quantifies the blood Hb level, is part of routine ANC (2). However, this and other available tests may be expensive, complex or impractical for use in rural or LMIC settings. A low-cost and reliable method of detecting anaemia is therefore needed for places with no or limited Access to laboratory facilities. WHO developed the haemoglobin colour scale, a low-cost method that is performed by placing a drop of undiluted blood on specially made chromatography paper and matching it against a range of colours representing different Hb values in 20 g/L increments (3). With haemoglobinometer tests, undiluted bloodis placed directly into a microcuvette, which is inserted into the haemoglobinometer (or photometer) to produce a reading (3)
The ANC recommendations are intended to inform the development of relevant health-care policies and clinical protocols. These recommendations were developed in accordance with the methods described in the WHO handbook for guideline development (4). In summary, the process included: identification of priority questions and outcomes, retrieval of evidence, assessment and synthesis of the evidence, formulation of recommendations, and planning for the implementation, dissemination, impact evaluation and updating of the guideline.
The quality of the scientific evidence underpinning the recommendations was graded using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) (5) and Confidence in the Evidence from Reviews of Qualitative research (GRADE-CERQual) (6) approaches, for quantitative and qualitative evidence, respectively. Up-to-date systematic reviews were used to prepare evidence profiles for priority questions. The DECIDE (Developing and Evaluating Communication Strategies to support Informed Decisions and Practice based on Evidence) (7) framework, an evidence-to-decision tool that includes intervention effects, values, resources, equity, acceptability and feasibility criteria, was used to guide the formulation and approval of recommendations by the Guideline Development Group (GDG) – an international group of experts assembled for the purpose of developing this guideline – at three Technical Consultations between October 2015 and March 2016.
To ensure that each recommendation is correctly understood and applied in practice, the context of all context-specific recommendations is clearly stated within each recommendation, and the contributing experts provided additional remarks where needed.
In accordance with WHO guideline development standards, these recommendations will be reviewed and updated following the identification of new evidence, with major reviews and updates at least every five years.
Further information on procedures for developing this recommendation are available here.
For this recommendation, we aimed to answer the following question:
The evidence was derived from a test accuracy review conducted to support the ANC guideline (2). Only one study (671 women) contributed data (8). The study, conducted in Malawi, assessed the test accuracy of on-site Hb testing with a haemoglobinometer (HemoCue®) and the HCS method in comparison to a full blood count test performed by an electronic counter (Coulter counter), the reference standard.
Moderate-certainty evidence shows that the sensitivity and specificity of the haemoglobinometer test in detecting anaemia (Hb < 110 g/L) are approximately 0.85 (95% CI: 0.79–0.90) and 0.80 (95% CI: 0.76–0.83), respectively, while the sensitivity and specificity of the HCS method are lower at approximately 0.75 (95% CI: 0.71–0.80) and 0.47 (95% CI: 0.41–0.53), respectively. For severe anaemia (defined in the study as Hb < 60 g/L), moderate-certainty evidence shows that the sensitivity and specificity of the haemoglobinometer test are approximately 0.83 (95% CI: 0.44–0.97) and 0.99 (95% CI: 0.98–1.00), respectively, while for the HCS method they are approximately 0.50 (95% CI: 0.15–0.85) and 0.98 (95% CI: 0.97–0.99), respectively.The technique included the use of both lower segment compression with one hand through the abdominal wall and bimanual lower segment and fundal compression through the abdominal wall.(9) The authors reported a decrease in the amount of blood loss in the group in which manual lower segment compression was used together with conventional management. Only one case report was found describing the bimanual abdominal/intravaginal technique.(10)
The main limitation of the evidence is the low number of women identified with severe anaemia, which affects the precision of the estimates. However, the evidence suggests that the haemoglobinometer test is probably more accurate than the HCS method. As there are no direct comparisons in test accuracy studies and, as confidence intervals for sensitivity and specificity of the two methods overlap, there is some uncertainty about the relative accuracy of these tests. The review also evaluated the test accuracy of clinical assessment (4 studies, 1853 women), giving a sensitivity for clinical assessment of 0.64 (95% CI: 22–94) and a specificity of 0.63 (95% CI: 23–91) for detecting anaemia (Hb < 110 g/L). Thus, the HCS method might be more sensitive but less specific than clinical assessment. In settings where iron supplementation is routinely used by pregnant women, the consequence of missing women with severe anaemia is more serious than that of missing women with mild or moderate anaemia, as women with severe anaemia usually require additional treatment. Therefore, the accuracy of on-site Hb tests to detect severe anaemia in pregnancy is probably more important than the ability to detect Hb below 110 g/L. A study of various Hb testing methods in Malawi found the haemoglobinometer method to be the most user-friendly method.
Further information on evidence supporting this recommendation are available here.
The GDG identified this research priority related to this recommendation
WHO recommendations on antenatal care for a positive pregnancy experience
Citation: WHO Reproductive Health Library. WHO recommendation on the method for diagnosing anaemia in pregnancy (December 2016). The WHO Reproductive Health Library; Geneva: World Health Organization.
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