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Hookworm-related anaemia among pregnant women: a systematic review.

Brooker S, Hotez PJ, Bundy DA - PLoS Negl Trop Dis (2008)

Bottom Line: All identified intervention studies showed a benefit of deworming for maternal or child health, but since a variety of outcomes measures were employed, quantitative evaluation was not possible.Evidence indicates that increasing hookworm infection intensity is associated with lower haemoglobin levels in pregnant women in poor countries.There are insufficient data to quantify the benefits of deworming, and further studies are warranted.

View Article: PubMed Central - PubMed

Affiliation: London School of Hygiene and Tropical Medicine, London, United Kingdom. simon.brooker@lshtm.ac.uk

ABSTRACT

Background and objectives: Hookworm infection is among the major causes of anaemia in poor communities, but its importance in causing maternal anaemia is poorly understood, and this has hampered effective lobbying for the inclusion of anthelmintic treatment in maternal health packages. We sought to review existing evidence on the role of hookworm as a risk factor for anaemia among pregnant women. We also estimate the number of hookworm infections in pregnant women in sub-Saharan Africa (SSA).

Methods: Structured searches using MEDLINE and EMBASE as well as manual searches of reference lists were conducted, and unpublished data were obtained by contacting authors. Papers were independently reviewed by two authors, and relevant data were extracted. We compared haemoglobin concentration (Hb) according to intensity of hookworm infection and calculated standardised mean differences and 95% confidence intervals. To estimate the number of pregnant women, we used population surfaces and a spatial model of hookworm prevalence.

Findings: One hundred and five reports were screened and 19 were eligible for inclusion: 13 cross-sectional studies, 2 randomised controlled trials, 2 non-randomised treatment trials and 2 observational studies. Comparing uninfected women and women lightly (1-1,999 eggs/gram [epg]) infected with hookworm, the standardised mean difference (SMD) was -0.24 (95% CI: -0.36 to -0.13). The SMD between women heavily (4000+ epg) infected and those lightly infected was -0.57 (95% CI: -0.87 to -0.26). All identified intervention studies showed a benefit of deworming for maternal or child health, but since a variety of outcomes measures were employed, quantitative evaluation was not possible. We estimate that 37.7 million women of reproductive age in SSA are infected with hookworm in 2005 and that approximately 6.9 million pregnant women are infected.

Conclusions: Evidence indicates that increasing hookworm infection intensity is associated with lower haemoglobin levels in pregnant women in poor countries. There are insufficient data to quantify the benefits of deworming, and further studies are warranted. Given that between a quarter and a third of pregnant women in SSA are infected with hookworm and at risk of preventable hookworm-related anaemia, efforts should be made to increase the coverage of anthelmintic treatment among pregnant women.

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Forest plot of the difference in haemoglobin (Hb) concentration among pregnant women women harbouring a light (1–1,999 eggs/gram) hookworm infection and women harbouring a heavy (4,000+ eggs/gram) infection.Standardised mean difference less than zero indicate lower Hb levels in heavily infected women compared to lightly infected women. The diamond represents the overall pooled estimates of the effect of heavy hookworm infection on Hb.
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pntd-0000291-g002: Forest plot of the difference in haemoglobin (Hb) concentration among pregnant women women harbouring a light (1–1,999 eggs/gram) hookworm infection and women harbouring a heavy (4,000+ eggs/gram) infection.Standardised mean difference less than zero indicate lower Hb levels in heavily infected women compared to lightly infected women. The diamond represents the overall pooled estimates of the effect of heavy hookworm infection on Hb.

Mentions: 13 studies presented observational data on the relationship between hookworm infection and haemoglobin concentration: eight from Africa, three from Asia and two from Latin America. The characteristics of the cross-sectional studies included are presented in Table 1. The data were stratified according to the intensity of infection. In four of the studies, none of the woman included had an intensity of infection that exceeded 2,000 epg; in eight studies women had an infection intensity that exceeded 4,000 epg. Comparing uninfected women and women lightly (1–1,999 epg) infected with hookworm, the standardized mean difference (SMD) in Hb was −0.72 (95% CI: −1.26 to −0.18) (n = 13), indicating that even women lightly infected with hookworm have lower Hb levels than uninfected women. However, there was variation in the differences observed and examination of forest plots suggested heterogeneity of effect, which was statistically significant (I2 score of 72.9%). This was explained by inclusion of the study by Rodríguez-Morales et al. [22] which collated data from nine states across Venezuela. Omitting this study from the analysis, the SMD between women uninfected and lightly infected was −0.24 (95% CI: −0.36 to −0.13) (Figure 1). Omission of other studies made little or no difference to the overall effect. There was slight evidence of bias using the Egger test (p = 0.008) and the Begg test (p = 0.07): the relatively small study by Ayoya et al. [23] in Mali showed evidence of effects that differed from the larger studies. Heavy hookworm infection was also significantly associated with a lower Hb level compared to light infection: the standardized mean difference in Hb was −0.57 (95% CI: −0.87 to −0.26) (n = 7) (Figure 2). No evidence of bias was observed.


Hookworm-related anaemia among pregnant women: a systematic review.

Brooker S, Hotez PJ, Bundy DA - PLoS Negl Trop Dis (2008)

Forest plot of the difference in haemoglobin (Hb) concentration among pregnant women women harbouring a light (1–1,999 eggs/gram) hookworm infection and women harbouring a heavy (4,000+ eggs/gram) infection.Standardised mean difference less than zero indicate lower Hb levels in heavily infected women compared to lightly infected women. The diamond represents the overall pooled estimates of the effect of heavy hookworm infection on Hb.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2553481&req=5

pntd-0000291-g002: Forest plot of the difference in haemoglobin (Hb) concentration among pregnant women women harbouring a light (1–1,999 eggs/gram) hookworm infection and women harbouring a heavy (4,000+ eggs/gram) infection.Standardised mean difference less than zero indicate lower Hb levels in heavily infected women compared to lightly infected women. The diamond represents the overall pooled estimates of the effect of heavy hookworm infection on Hb.
Mentions: 13 studies presented observational data on the relationship between hookworm infection and haemoglobin concentration: eight from Africa, three from Asia and two from Latin America. The characteristics of the cross-sectional studies included are presented in Table 1. The data were stratified according to the intensity of infection. In four of the studies, none of the woman included had an intensity of infection that exceeded 2,000 epg; in eight studies women had an infection intensity that exceeded 4,000 epg. Comparing uninfected women and women lightly (1–1,999 epg) infected with hookworm, the standardized mean difference (SMD) in Hb was −0.72 (95% CI: −1.26 to −0.18) (n = 13), indicating that even women lightly infected with hookworm have lower Hb levels than uninfected women. However, there was variation in the differences observed and examination of forest plots suggested heterogeneity of effect, which was statistically significant (I2 score of 72.9%). This was explained by inclusion of the study by Rodríguez-Morales et al. [22] which collated data from nine states across Venezuela. Omitting this study from the analysis, the SMD between women uninfected and lightly infected was −0.24 (95% CI: −0.36 to −0.13) (Figure 1). Omission of other studies made little or no difference to the overall effect. There was slight evidence of bias using the Egger test (p = 0.008) and the Begg test (p = 0.07): the relatively small study by Ayoya et al. [23] in Mali showed evidence of effects that differed from the larger studies. Heavy hookworm infection was also significantly associated with a lower Hb level compared to light infection: the standardized mean difference in Hb was −0.57 (95% CI: −0.87 to −0.26) (n = 7) (Figure 2). No evidence of bias was observed.

Bottom Line: All identified intervention studies showed a benefit of deworming for maternal or child health, but since a variety of outcomes measures were employed, quantitative evaluation was not possible.Evidence indicates that increasing hookworm infection intensity is associated with lower haemoglobin levels in pregnant women in poor countries.There are insufficient data to quantify the benefits of deworming, and further studies are warranted.

View Article: PubMed Central - PubMed

Affiliation: London School of Hygiene and Tropical Medicine, London, United Kingdom. simon.brooker@lshtm.ac.uk

ABSTRACT

Background and objectives: Hookworm infection is among the major causes of anaemia in poor communities, but its importance in causing maternal anaemia is poorly understood, and this has hampered effective lobbying for the inclusion of anthelmintic treatment in maternal health packages. We sought to review existing evidence on the role of hookworm as a risk factor for anaemia among pregnant women. We also estimate the number of hookworm infections in pregnant women in sub-Saharan Africa (SSA).

Methods: Structured searches using MEDLINE and EMBASE as well as manual searches of reference lists were conducted, and unpublished data were obtained by contacting authors. Papers were independently reviewed by two authors, and relevant data were extracted. We compared haemoglobin concentration (Hb) according to intensity of hookworm infection and calculated standardised mean differences and 95% confidence intervals. To estimate the number of pregnant women, we used population surfaces and a spatial model of hookworm prevalence.

Findings: One hundred and five reports were screened and 19 were eligible for inclusion: 13 cross-sectional studies, 2 randomised controlled trials, 2 non-randomised treatment trials and 2 observational studies. Comparing uninfected women and women lightly (1-1,999 eggs/gram [epg]) infected with hookworm, the standardised mean difference (SMD) was -0.24 (95% CI: -0.36 to -0.13). The SMD between women heavily (4000+ epg) infected and those lightly infected was -0.57 (95% CI: -0.87 to -0.26). All identified intervention studies showed a benefit of deworming for maternal or child health, but since a variety of outcomes measures were employed, quantitative evaluation was not possible. We estimate that 37.7 million women of reproductive age in SSA are infected with hookworm in 2005 and that approximately 6.9 million pregnant women are infected.

Conclusions: Evidence indicates that increasing hookworm infection intensity is associated with lower haemoglobin levels in pregnant women in poor countries. There are insufficient data to quantify the benefits of deworming, and further studies are warranted. Given that between a quarter and a third of pregnant women in SSA are infected with hookworm and at risk of preventable hookworm-related anaemia, efforts should be made to increase the coverage of anthelmintic treatment among pregnant women.

Show MeSH
Related in: MedlinePlus