Association of anaemia in primary care patients with chronic kidney disease: cross sectional study of quality improvement in chronic kidney disease (QICKD) trial data

Background: Anaemia is a known risk factor for cardiovascular disease and treating anaemia in chronic kidney disease (CKD) may improve outcomes. However, little is known about the scope to improve primary care management of anaemia in CKD. Methods: An observational study (N = 1,099,292) with a nationally representative sample using anonymised routine primary care data from 127 Quality Improvement in CKD trial practices (ISRCTN5631023731). We explored variables associated with anaemia in CKD: eGFR, haemoglobin (Hb), mean corpuscular volume (MCV), iron status, cardiovascular comorbidities, and use of therapy which associated with gastrointestinal bleeding, oral iron and deprivation score. We developed a linear regression model to identify variables amenable to improved primary care management. Results: The prevalence of Stage 3-5 CKD was 6.76%. Hb was lower in CKD (13.2 g/dl) than without (13.7 g/dl). 22.2% of people with CKD had World Health Organization defined anaemia; 8.6% had Hb <= 11 g/dl; 3% Hb <= 10 g/dl; and 1% Hb <= 9 g/dl. Normocytic anaemia was present in 80.5% with Hb <= 11; 72.7% with Hb <= 10 g/dl; and 67.6% with Hb <= 9 g/dl; microcytic anaemia in 13.4% with Hb <= 11 g/dl; 20.8% with Hb <= 10 g/dl; and 24.9% where Hb <= 9 g/dl. 82.7% of people with microcytic and 58.8% with normocytic anaemia (Hb <= 11 g/dl) had a low ferritin (< 100ug/mL). Hypertension (67.2% vs. 54%) and diabetes (30.7% vs. 15.4%) were more prevalent in CKD and anaemia; 61% had been prescribed aspirin; 73% non-steroidal anti-inflammatory drugs (NSAIDs); 14.1% warfarin 12.4% clopidogrel; and 53.1% aspirin and NSAID. 56.3% of people with CKD and anaemia had been prescribed oral iron. The main limitations of the study are that routine data are inevitably incomplete and definitions of anaemia have not been standardised. Conclusions: Medication review is needed in people with CKD and anaemia prior to considering erythropoietin or parenteral iron. Iron stores may be depleted in over > 60% of people with normocytic anaemia. Prescribing oral iron has not corrected anaemia.