Assessment of haemoglobin and serum markers of iron deficiency in people with cardiovascular disease

Abstract

Background: The prevalence of anaemia and iron deficiency and their prognostic association with cardiovascular disease have rarely been explored at population level.

Methods: National Health Service records of the Greater Glasgow region for patients aged ≥50 years with a broad range of cardiovascular diagnoses were obtained. During 2013/14, prevalent disease was identified and results of investigations collated. Anaemia was defined as haemoglobin <13 g/dL for men or <12 g/dL for women. Incident heart failure, cancer and death between 2015 and 2018 were identified.

Results: The 2013/14 dataset comprised 197 152 patients, including 14 335 (7%) with heart failure. Most (78%) patients had haemoglobin measured, especially those with heart failure (90%). Of those tested, anaemia was common both in patients without (29%) and with heart failure (prevalent cases in 2013/14: 46%; incident cases during 2013/14: 57%). Ferritin was usually measured only when haemoglobin was markedly depressed; transferrin saturation (TSAT) even less often. Incidence rates for heart failure and cancer during 2015-18 were inversely related to nadir haemoglobin in 2013/14. A haemoglobin of 13-15 g/dL for women and 14-16 g/dL for men was associated with the lowest mortality. Low ferritin was associated with a better prognosis and low TSAT with a worse prognosis.

Conclusion: In patients with a broad range of cardiovascular disorders, haemoglobin is often measured but, unless anaemia is severe, markers of iron deficiency are usually not. Low haemoglobin and TSAT, but not low ferritin, are associated with a worse prognosis. The nadir of risk occurs at haemoglobin 1-3 g/dL above the WHO definition of anaemia.

Keywords: biomarkers; electronic health records; epidemiology; heart failure.

Figure 1

Testing patterns of iron biomarkers according to haemoglobin concentration. Ferritin on the left and, separately on the right, serum iron or transferrin saturation (TSAT) according to haemoglobin concentrations and patient group (not heart failure (HF); incident HF; prevalent HF). Numbers are presented below each graph.

Figure 2

Unadjusted Kaplan-Meier survival curves and corresponding forest plots showing associations between haemoglobin (Hb) concentrations and mortality from 1 January 2015 to 31 March 2018 in patients without heart failure recorded at any time. Numbers at risk presented with each Kaplan-Meier and age-adjusted and sex-adjusted HRs with corresponding 95% CIs also presented.

Figure 3

Unadjusted Kaplan-Meier survival curves and corresponding forest plots showing associations between haemoglobin (Hb) concentrations and mortality from 1 January 2015 to 31 March 2018 in patients with incident heart failure between 1 January 2013 and 31 December 2014. Numbers at risk presented with each Kaplan-Meier and age-adjusted and sex-adjusted HRs with corresponding 95% CIs also presented.

Figure 4

Unadjusted Kaplan-Meier survival curves and corresponding forest plots showing associations between haemoglobin (Hb) concentrations and mortality from 1 January 2015 to 31 March 2018 in patients with prevalent heart failure prior to 1 January 2013. Numbers at risk presented with each Kaplan-Meier and age-adjusted and sex-adjusted HRs with corresponding 95% CIs also presented.

Figure 5

Mortality of patients without a history of heart failure by concentrations of serum ferritin (Ferr). Forest plots showing all-cause mortality from 1 January 2015 to 31 March 2018 for patients without a history of heart failure during, or prior to, 2013/14 according to concentrations of serum Ferr (not measured; >300 µg/L; 100–300 µg/L; 30–100 µg/L; <30 µg/L). Age-adjusted and sex-adjusted HRs with corresponding 95% CIs are presented.

Figure 6

Mortality of patients without a history of heart failure by transferrin saturation (TSAT) (%). Forest plots showing all-cause mortality from 1 January 2015 to 31 March 2018 for patients without a history of heart failure during, or prior to, 2013/14 according to TSAT (%) (not measured; ≥50%; 40%–49%; 30%–39%; 20%–29%; 10%–19%; <10%). Age-adjusted and sex-adjusted HRs with corresponding 95% CIs are presented.