Chi 2021.

Study characteristics
Methods	Study characteristics Study design: parallel RCT Study duration: September 2017 to July 2019 Study follow‐up: 12 weeks
Participants	Baseline characteristics Country: China Setting: university hospital (1 site) Inclusion criteria: maintenance HD patients; Hb < 120 g/L (male) and Hb < 110 g/L (female); able to undergo HD in hospital; ≥ 60 years; duration of HD ≥ 2 years; duration of low‐flux HD ≥ 3 months; absence of severe infection or heart failure, antibiotic treatment, active diseases, and malignant tumours in the past 3 months; taking low‐molecular‐weight heparin calcium anticoagulation; undergoing 3 x 4‐hour HD/week and blood flow 200 to 300 mL/min; smooth blood circulation during dialysis, reaching or approaching the dry body mass; good treatment compliance Randomised number (intervention 1/intervention 2/intervention 3): 25/25/25 Dialysis modality: HD Mean age ± SD (years): intervention group 1 (71.08 ± 9.18); intervention group 2 (71.2 ± 6.31); intervention group 3 (71.32 ± 7.12) Sex (M/F): intervention group 1 (14/11); intervention group 2 (15/10); intervention group 3 (13/12) Dialysis duration: not reported Exclusion criteria: use of glucocorticoids or immunosuppressants in the past 3 months; bleeding or blood transfusion or taking antibiotics in the past 3 months; haematologic disease; acute or chronic infection; severe malnutrition; malignant tumours; severe heart failure or multiple organ failure; sepsis, chronic hepatitis, tuberculosis, systemic lupus erythematosus, vasculitis, liver insufficiency, epilepsy, a family history of epilepsy; blood flow during dialysis < 200 mL/min
Interventions	Intervention group 1 L‐carnitine (IV): 1000 mg at each dialysis session for 12 weeks High‐flux: ultrafiltration coefficient 59 mL/(h·mm Hg) and an effective surface area of 1.8 m² Intervention group 2 High‐flux: ultrafiltration coefficient 59 mL/(h·mm Hg) and an effective surface area of 1.8 m² Intervention group 3 Low‐flux: ultrafiltration coefficient 12 mL/(h·mm Hg) and an effective surface area of 1.4 m²
Outcomes	Outcomes relevant to this review Adverse events Anaemia‐related markers: Hb
Notes	Funding source: the Zhongshan Science and Technology Bureau Projects
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "divided by numeration table into three groups"
Allocation concealment (selection bias)	Unclear risk	Insufficient information to permit judgement
Blinding of participants and personnel (performance bias)	Unclear risk	Insufficient information to permit judgement
Blinding of outcome assessment (detection bias) Adverse events	Unclear risk	Insufficient information to permit judgement
Blinding of outcome assessment (detection bias) Anaemia‐related markers	Low risk	The outcome measurement is not likely to be influenced by lack of blinding
Incomplete outcome data (attrition bias) Adverse events	Low risk	All patient outcome data reported
Incomplete outcome data (attrition bias) Anaemia‐related markers	Low risk	All patient outcome data reported
Selective reporting (reporting bias)	Unclear risk	Insufficient information to permit judgement
Other bias	Low risk	Funding source: the Zhongshan Science and Technology Bureau Projects