Kidney involvement and anemia in COVID-19 infection

Table 3 Anemia treatment strategies in renal disease patients (all chronic kidney disease stages, dialysis, transplant) who also have COVID-19 infection/systemic inflammation

CKD stage/modality	eGFR range (mL/min/1.73 m²)	Iron therapy	ESAs/HIFi	Anemia assessment monitoring frequency	Target Hb (g/dL)	Additional notes
Stage 1	≥ 90	Not routinely required unless iron deficiency is confirmed	Rarely indicated	Annually	11-12	Investigate other causes of anemia. Also evaluate: Blood smear review, haptoglobin, LDH, CRP, vitamin B12, folate, liver enzymes, SPEP with immunofixation, serum-free light chains, urinary Bence-Jones protein. TSH and stool analysis
Stage 2	60-89	Oral iron if ferritin < 100 ng/mL or TSAT < 20%. Withhold iron if ferritin ≥ 700 ng/mL (≥ 700 µg/L) or TSAT ≥ 40%	Usually not required	2times/yr	11-12	Nutritional assessment recommended
Stage 3	30-59	Oral or IV iron if ferritin < 100 ng/mL (< 100 µg/L) and transferrin saturation (TSAT) < 40%, or ferritin ≥ 100 ng/mL (≥ 100 µg/L) and < 300 ng/mL (< 300 µg/L), and TSAT < 25%. Withhold iron if ferritin ≥ 700 ng/mL (≥ 700 µg/L) or TSAT ≥ 40%	Consider if Hb < 10 g/dL	2-3 times/yr	10-11.5	Start addressing potential ESA/HIF-PHIi need
Stage 4	15-29	IV iron preferred, start therapy if ferritin < 100 ng/mL (< 100 µg/L) and transferrin saturation (TSAT) < 40%, or ferritin ≥ 100 ng/mL (≥ 100 µg/L) and < 300 ng/mL (< 300 µg/L), and TSAT < 25%. Withhold iron if ferritin ≥ 700 ng/mL (≥ 700 µg/L) or TSAT ≥ 40%	Initiate if Hb < 10 and iron replete	Quarterly	10-11.5	Monitor for ESA/HIF-PHIi resistance, inflammation
Stage 5 (non-dialysis)	< 15	Oral or IV iron. Withhold iron if ferritin ≥ 700 ng/mL (≥ 700 µg/L) or TSAT ≥ 40%	Usually required	Monthly to quarterly	10-11.5	Prepare for dialysis transition. Monitor for ESA/HIF-PHIi resistance, inflammation
Peritoneal dialysis	N/A	Oral or IV iron if ferritin < 100 ng/mL (< 100 µg/L) and transferrin saturation (TSAT) < 40%, or ferritin ≥ 100 ng/mL (≥ 100 µg/L) and < 300 ng/mL (< 300 µg/L), and TSAT < 25%. Withhold iron if ferritin ≥ 700 ng/mL (≥ 700 µg/L) or TSAT ≥ 40%	Commonly required	Monthly	10-11.5	Monitor for ESA/HIF-PHIi resistance, inflammation
Hemodialysis	N/A	IV iron (standard of care). Initiating iron therapy if ferritin ≤ 500 ng/mL (≤ 500 µg/L) and TSAT ≤ 30%. Withhold iron if ferritin ≥ 700 ng/mL (≥ 700 µg/L) or TSAT ≥ 40%	Required regularly	Monthly	10-11.5	Blood losses during HD contribute to anemia. Monitor for ESA/HIF-PHIi resistance, inflammation
Kidney transplant	N/A	Iron supplementation if deficiency persists. Withhold iron if ferritin ≥ 700 ng/mL (≥ 700 µg/L) or TSAT ≥ 40%	Rare post-transplant unless chronic graft dysfunction	Every 3-6 mo	11-12	Anemia often improves, but monitor for graft rejection or chronic disease recurrence, pharmacological interactions

The table focuses on the modifications needed due to inflammation and infection, including ESAs resistance, iron metabolism changes, and safety considerations. CRP: C-reactive protein; CKD: Chronic kidney disease; CRP: C-reactive protein; ESAs: Erythropoiesis-stimulating agents; eGFR: Estimated glomerular filtration rate; HD: Hemodialysis; Hb: Hemoglobin; HIF-PHI: Hypoxia-inducible factor prolyl hydroxylase inhibitor; IV: Intravenous; LDH: Lactate dehydrogenase; SPEP: Serum protein electrophoresis; TSH: Thyroid-stimulating hormone; TSAT: Transferrin saturation.