Sex specific definitions of anaemia contribute to health inequity and sociomedical injustice

The origin of ferritin reference intervals: a systematic review

Iron deficiency is a highly prevalent condition, which contributes to unnecessary morbidity, mortality, and health inequity. A serum ferritin concentration of less than 30 μg/L has a high specificity and sensitivity for diagnosing iron deficiency in adults, but the laboratory reported lower limit of normal (LLN) is typically lower. These LLNs might not be rooted in rigorous scientific evidence and might be contributing to structural underdiagnosis of iron deficiency. A systematic review was done per systematic reviews and meta-analysis guidelines with the use of medical literature databases from inception of each database to Nov 30, 2021, to identify studies that determined ferritin reference intervals in healthy adults and grey literature search for the five most common ferritin assays (registration number CRD42022268844). The objectives were to systematically summarise the ferritin reference intervals and to do a methodological quality assessment of the included studies. 2306 studies were screened and 61 full texts were included. 37 studies were eligible for analysis of the ferritin LLN in the general population. The population the sample was comprised of was a total of 21 882 females and 23 650 males participants. The ferritin LLN was a median of 8 μg/L (IQR 5-15) and mean of 9 μg/L (SD 11) in females and a median of 25 μg/L (IQR 16-44) and mean of 25 μg/L (SD 29) in males. 30 (49%) of 61 studies did not explicitly screen for patients at risk of iron deficiency, and 32 (52%) did not refer to a reference interval establishment guideline (eg, guideline recommended by Clinical and Laboratory Standards Institute). The five most used commercial ferritin laboratory assays reported reference intervals with a median LLN of 11 (IQR 9-12) and mean of 9 μg/L (SD 4) for females and median of 22 (IQR 22-24) and mean of 23 μg/L (SD 4) for males. In the literature, serum ferritin reference intervals in healthy adults consistently report a LLN of less than 30 μg/L. Data driving these ferritin reference intervals are at high risk of bias, given no exclusion of individuals at risk for iron deficiency in the presumed normal population sample and no adherence to reference interval establishment standards. We suggest the use of evidence-based laboratory clinical decision limits to diagnose iron deficiency.

Iron Deficiency Among Hospitalized Patients With Congestive Heart Failure

INTRODUCTION

Studies have demonstrated the efficacy of intravenous (IV) iron when administered to patients with congestive heart failure (CHF) and iron deficiency (ID). We aimed to better understand the adherence of treatment for ID among a population with CHF, with particular interest in high-risk groups not often studied due to inadequate recruitment.

METHODS

A retrospective chart review at our institution was conducted from January 1, 2012, to July 7, 2021. Analysis included hospitalized patients with CHF and ID and dividing these patients into two time periods based on changes in iron treatment patterns and treatment between sexes.

RESULTS

Four thousand eight hundred thirteen patients were included in this study. During the "early era," 7.0% of patients with CHF and ID received IV iron compared with 20.9% of "late-era" patients. Female patients with ID were statistically less likely to receive IV iron when compared with male patients, both unadjusted (0.66, confidence interval [CI] 0.55-0.79, p < .0001) and adjusted (0.72, CI 0.59-0.87, p < .0001) for covariates.

CONCLUSION

This study illustrates improved adherence to treatment for ID among hospitalized population with CHF and ID over time but persistent undertreatment remains. Future studies will need to identify the barriers to treating female patients with CHF and ID to reduce these disparities.

Age-specific sex-differences in cerebral blood flow velocity in relation to haemoglobin levels

INTRODUCTION

Cerebral blood flow (CBF) declines with age and abnormalities in CBF are associated with age-related cerebrovascular disease and neurodegeneration. Women have higher CBF than men, although this sex-difference diminishes to some extent with age in healthy subjects. The physiological drivers of these age/sex differences are uncertain, but might be secondary to age and sex-differences in haemoglobin (Hb) level. Hb levels are inversely correlated with CBF, are lower in women, and decline with age in men, but the interrelations between these factors have not been explored systematically either in healthy subjects or across the full age-range in patients with vascular risk factors. We aimed to determine the age-specific interrelations between sex, Hb, and CBF velocity in a large cohort of patients with cerebrovascular disease.

PATIENTS AND METHODS

In patients with a recent transient ischaemic attack or minor stroke (Oxford Vascular Study) and no ipsilateral or contralateral stenosis of the carotid or intracranial arteries, we related peak-systolic velocity (PSV) and other parameters on transcranial Doppler ultrasound (TCD) of the middle cerebral artery to sex, age, Hb and vascular risk factors.

RESULTS

Of 958 eligible subjects (mean age/SD = 68.04/14.26, 53.2% male), younger women (age < 55 years) had higher CBF velocities than men (mean sex difference in PSV at age < 55 years = 16.31 cm/s; p < 0.001), but this difference declined with age (interaction p < 0.001), such that it was no longer significant at age 75-84 (∆PSV = 3.26 cm/s; p = 0.12) and was reversed at age ⩾ 85 (∆PSV = -7.42 cm/s; p = 0.05). These changes mirrored trends in levels of Hb, which were higher in men at age < 55 (∆Hb = 1.92 g/dL; p < 0.001), but steadily decreased with age in men but not in women (interaction p < 0.001), with no residual sex-difference at age ⩾ 85 (∆Hb = 0.12 g/dL; p = 0.70). There was an inverse correlation between Hb and PSV in both women and men (both p ⩽ 0.01), and the sex-difference in PSV at age < 55 was substantially diminished after adjustment for Hb (∆PSV = 6.92; p = 0.036; ∆PSV = 5.92, p = 0.13 with further adjustment for end-tidal CO2). In contrast, the sex difference in PSV was unaffected by adjustment for systolic and diastolic blood pressure, heart rate, and vascular risk factors (history of hypertension, diabetes, hyperlipidaemia and smoking).

DISCUSSION

CBF velocity is strongly correlated with Hb level at all ages, and sex-differences in CBF velocity appear to be explained in major part by age-related sex-differences in Hb.

Haemoglobin thresholds to define anaemia from age 6 months to 65 years: estimates from international data sources

BACKGROUND

Detection of anaemia is crucial for clinical medicine and public health. Current WHO anaemia definitions are based on statistical thresholds (fifth centiles) set more than 50 years ago. We sought to establish evidence for the statistical haemoglobin thresholds for anaemia that can be applied globally and inform WHO and clinical guidelines.

METHODS

In this analysis we identified international data sources from populations in the USA, England, Australia, China, the Netherlands, Canada, Ecuador, and Bangladesh with sufficient clinical and laboratory information collected between 1998 and 2020 to obtain a healthy reference sample. Individuals with clinical or biochemical evidence of a condition that could reduce haemoglobin concentrations were excluded. We estimated haemoglobin thresholds (ie, 5th centiles) for children aged 6-23 months, 24-59 months, 5-11 years, and 12-17 years, and adults aged 18-65 years (including during pregnancy) for individual datasets and pooled across data sources. We also collated findings from three large-scale genetic studies to summarise genetic variants affecting haemoglobin concentrations in different ancestral populations.

FINDINGS

We identified eight data sources comprising 18 individual datasets that were eligible for inclusion in the analysis. In pooled analyses, the haemoglobin fifth centile was 104·4 g/L (90% CI 103·5-105·3) in 924 children aged 6-23 months, 110·2 g/L (109·5-110·9) in 1874 children aged 24-59 months, and 114·4 g/L (113·6-115·2) in 1839 children aged 5-11 years. Values diverged by sex in adolescents and adults. In pooled analyses, the fifth centile was 122·2 g/L (90% CI 121·3-123·1) in 1741 female adolescents aged 12-17 years and 128·2 g/L (126·4-130·0) in 1103 male adolescents aged 12-17 years. In pooled analyses of adults aged 18-65 years, the fifth centile was 119·7 g/L (90% CI 119·1-120·3) in 3640 non-pregnant females and 134·9 g/L (134·2-135·6) in 2377 males. Fifth centiles in pregnancy were 110·3 g/L (90% CI 109·5-111·0) in the first trimester (n=772) and 105·9 g/L (104·0-107·7) in the second trimester (n=111), with insufficient data for analysis in the third trimester. There were insufficient data for adults older than 65 years. We did not identify ancestry-specific high prevalence of non-clinically relevant genetic variants that influence haemoglobin concentrations.

INTERPRETATION

Our results enable global harmonisation of clinical and public health haemoglobin thresholds for diagnosis of anaemia. Haemoglobin thresholds are similar between sexes until adolescence, after which males have higher thresholds than females. We did not find any evidence that thresholds should differ between people of differering ancestries.

FUNDING

World Health Organization and the Bill & Melinda Gates Foundation.

Iron deficiency anemia among women: An issue of health equity

Iron deficiency is the most common and widespread nutritional deficiency in the world. For women, the risk of iron deficiency and iron deficiency anemia increases due to iron demands during pregnancy and regular iron losses due to menstruation during reproductive years. These interrelated conditions are of public health concern as they are highly prevalent, and the negative consequences such as chronic fatigue, cognitive impairment and poor quality of life are broad and multifaceted. People of low socioeconomic status are at higher risk of iron deficiency due to low intake of expensive iron-rich foods, and decreased access to healthcare. In this review, we applied a health equity lens to describe the current state of care for women with iron deficiency with or without anemia. We have highlighted several structural challenges that span from the laboratory diagnosis, inconsistent screening guidelines, and stigma associated with heavy menstrual bleeding, to treatment barriers.

Prevalence of Iron Deficiency and Iron-Deficiency Anemia in US Females Aged 12-21 Years, 2003-2020

This study examines prevalence of iron deficiency among females aged 12 to 21 years to inform future screening strategies for iron deficiency and iron-deficiency anemia.

Statistical haemoglobin thresholds to define anaemia across the lifecycle

Detection of anaemia is critical for clinical medicine and public health. Current WHO values that define anaemia are statistical thresholds (5 ^th centile) set over 50 years ago, and are presently <110g/L in children 6-59 months, <115g/L in children 5-11 years, <110g/L in pregnant women, <120g/L in children 12-14 years of age, <120g/L in non-pregnant women, and <130g/L in men. Haemoglobin is sensitive to iron and other nutrient deficiencies, medical illness and inflammation, and is impacted by genetic conditions; thus, careful exclusion of these conditions is crucial to obtain a healthy reference population. We identified data sources from which sufficient clinical and laboratory information was available to determine an apparently healthy reference sample. Individuals were excluded if they had any clinical or biochemical evidence of a condition that may diminish haemoglobin concentration. Discrete 5 ^th centiles were estimated along with two-sided 90% confidence intervals and estimates combined using a fixed-effect approach. Estimates for the 5 ^th centile of the healthy reference population in children were similar between sexes. Thresholds in children 6-23 months were 104.4g/L [90% CI 103.5, 105.3]; in children 24-59 months were 110.2g/L [109.5, 110.9]; and in children 5-11 years were 114.1g/L [113.2, 115.0]. Thresholds diverged by sex in adolescents and adults. In females and males 12-17 years, thresholds were 122.2g/L [121.3, 123.1] and 128.2 [126.4, 130.0], respectively. In adults 18-65 years, thresholds were 119.7g/L [119.1, 120.3] in non-pregnant females and 134.9g/L [134.2, 135.6] in males. Limited analyses indicated 5 ^th centiles in first-trimester pregnancy of 110.3g/L [109.5, 111.0] and 105.9g/L [104.0, 107.7] in the second trimester. All thresholds were robust to variations in definitions and analysis models. Using multiple datasets comprising Asian, African, and European ancestries, we did not identify novel high prevalence genetic variants that influence haemoglobin concentration, other than variants in genes known to cause important clinical disease, suggesting non-clinical genetic factors do not influence the 5 ^th centile between ancestries. Our results directly inform WHO guideline development and provide a platform for global harmonisation of laboratory, clinical and public health haemoglobin thresholds.

Daily versus every other day oral iron supplementation in patients with iron deficiency anemia (DEODO): study protocol for a phase 3 multicentered, pragmatic, open-label, pilot randomized controlled trial

BACKGROUND

Iron deficiency anemia (IDA) accounts for the majority of anemia cases across the globe and can lead to impairments in both physical and cognitive functioning. Oral iron supplementation is the first line of treatment to improve the hemoglobin level for IDA patients. However, gaps still exist in understanding the appropriate dosing regimen of oral iron. The current trial proposes to evaluate the feasibility of performing this study to examine the effectiveness and side-effect profile of oral iron once daily versus every other day.

METHODS

In this open-label, pilot, feasibility, randomized controlled trial, 52 outpatients over 16 years of age with IDA (defined as hemoglobin < 12.0 g/dL in females and < 13.0 g/dL in males and ferritin < 30 mcg/L) will be enrolled across two large academic hospitals. Participants are randomized in a 1:1 ratio to receive 300 mg oral ferrous sulfate (60 mg of elemental iron) either every day or every other day for 12 weeks. Participants are excluded if they are as follows: (1) pregnant and/or currently breastfeeding, (2) have a disease history that would impair response to oral iron (e.g., thalassemia, celiac disease), (3) intolerant and/or have an allergy to oral iron or vitamin C, (4) on new anticoagulants in the past 6 months, (5) received IV iron therapy in the past 12 weeks, (6) have surgery, chemotherapy, or blood donation planned in upcoming 12 weeks, (7) a creatinine clearance < 30 mL/min, or (8) hemoglobin less than 8.0 g/dL with active bleeding. The primary outcome is feasibility to enroll 52 participants in this trial over a 2-year period to determine the effectiveness of daily versus every other day oral iron supplementation on hemoglobin at 12 weeks post-initiation and side-effect profile.

DISCUSSION

The results of this trial will provide additional evidence for an appropriate dosing schedule for treating patients with IDA with oral iron supplementation. Additional knowledge will be gained on how the dosing regimen of oral iron impacts quality of life and hemoglobin repletion in IDA patients. If this trial is deemed feasible, it will inform the development and implementation of a larger multicenter definitive trial.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT03725384 . Registered 31 October 2018.