Table 1. Population data table.

LVEF- Left ventricular ejection fraction; Hb- Hemoglobin; HF- Heart failure; WHO- World Health Organization; COMET- Comparing an Operation to Monitoring, With or Without Endocrine Therapy; NYHA- New York Heart Association; ICD- International classification of diseases 

Klip et al. (2013) [9]; Schou et al. (2007) [34]; Komajda et al. (2006); [35] Kosiborod et al. (2005) [36]; Anand et al. (2004) [37]; Ezekowitz et al. (2003) [38]; Horwich et al. (2002) [40]

References	Study design	Population and setting	Cases of HF	Prevalence of anemia	HF classification	Criteria for diagnosis of anemia	Conclusion
Klip et al. (2013)	Prospective observational, multicenter cohort study	Patients from 5 cohorts from Poland, Spain and The Netherlands	1,506	426	Reduced or preserved LVEF	Hb <13 g/dL for men and <12 g/dL for women (WHO criteria) [2]	Iron deficiency is a common finding in HF patients and is associated with the severity of the disease.
Schou et al. (2007)	Prospective, observational, single-center cohort study	Outpatients with Systolic Heart Failure in Frederiksberg University Hospital, Denmark	345	27%	Systolic HF (LVEF <45%)	WHO criteria	Anemia is associated with an increased risk of mortality in HF patients.
Komajda et al. (2006)	Secondary analysis of clinical trial (COMET)	Participants of the COMET trial	3029	482	NYHA class II to IV and LVEF ≤35%	WHO criteria	Anemia is associated with increased hospital admissions and mortality in HF patients.
Kosiborod et al. (2005)	Retrospective observational, multicenter cohort study	Age of 65 years and older from NHC Project sample	50,405	Men -61.2%   Women- 52.1%	History of documented HF. Radiographic evidence of HF.	Hematocrit of < 40% for men and < 37% for women.	Anemia is associated with heart failure and may be a marker of increased mortality in HF patients.
Anand et al. (2004)	Multicenter, double-blind, placebo-controlled RENAISSANCE trial	Age of  18 to 55 years in North America	912	12%	NYHA class II to IV	Hb≤12.0g/dL	Anemia is a common finding in patients with HF and is associated with poorer prognosis and greater mortality rates.
Ezekowitz et al. (2003)	Population-based cohort study	Median age of 78 in Alberta, Canada	12,065	17%	ICD-9 Code 428.x [39]	ICD-9 codes 280-289 [39]	Anemia is a common finding in patients with heart failure and is associated with poorer prognosis and mortality.
Horwich et al. (2002)	Prospective, observational, single-center cohort study	Patients referred to a single University Medical Center in University of California, Los Angeles, USA	1,061	30%	NYHA class III or IV and LVEF <40%	WHO criteria	Anemia is associated with poorer prognosis and greater mortality rates in patients of HF.