The clinical significance of anaemia and disturbed iron homeostasis in chronic respiratory failure.

BACKGROUND

Anaemia is a frequent, clinically relevant condition in various chronic diseases. It seems also to be prevalent in patients with chronic respiratory failure (CRF). We studied the characteristics of anaemia in CRF and its associations with clinical outcome.

METHODS

In a prospective design, 271 consecutive patients with CRF were evaluated; patients with other conditions often associated with anaemia were excluded. Haematological laboratory and physiological parameters, health-related quality of life (HRQL), dyspnoea and 48-month survival were determined. Anaemia was defined according to WHO [haemoglobin (Hb)< 13 g/l (male); Hb< 12 g/dl (female)] and using an established algorithm.

RESULTS

Among 185 patients included, 18.4% showed anaemia, not depending on chronic obstructive pulmonary disease (COPD) vs. non-COPD (17.6% vs. 19.0%; p = 0.851) or on gender [16.5% (female) vs. 19.8% (male); p = 0.702]. Anaemic patients had higher age, creatinine (p < 0.05 each) and erythropoietin levels (p < 0.001), but lower transferrin saturation (TSAT), serum iron and vitamin B12 levels (p < 0.01 each). By definition, most anaemic patients (67.6%) had disturbances in iron homeostasis according to 'anaemia of chronic disease' and/or true iron deficiency anaemia. Hb was independently related to dyspnoea and HRQL, while TSAT ≥ 20% was linked to less dyspnoea and better subjective exercise capability. Non-survivors had lower Hb and serum iron levels (p < 0.05 each). In multivariate analysis, lower serum iron levels and TSAT were independently associated with mortality (p < 0.05 each).

CONCLUSION

Anaemia was common in patients with CRF and often because of disturbed iron homeostasis. Hb and TSAT were linked to functional outcome and HRQL. Lower serum iron levels and TSAT were independent prognostic parameters.