Glycated Hemoglobin and Risk of Death in Diabetic Patients Treated With Hemodialysis: A Meta-analysis

Background: Studies investigating the association between glycated hemoglobin (HbA) level and mortality risk in diabetic patients receiving hemodialysis have shown conflicting results. 
Study Design: We conducted a systematic review and meta-analysis using MEDLINE, EMBASE, Web of Science, and the Cochrane Library. 
Setting & Population: Diabetic patients on maintenance hemodialysis therapy. 
Selection Criteria for Studies: Observational studies or randomized controlled trials investigating the association between HbA values and mortality risk. Study authors were asked to provide anonymized individual patient data or reanalyze results according to a standard template. 
Predictor: Single measurement or mean HbA values. Mean HbA values were calculated using all individual-patient HbA values during the follow-up period of contributing studies. 
Outcome: HR for mortality risk. 
Results: 10 studies (83,684 participants) were included: 9 observational studies and one secondary analysis of a randomized trial. After adjustment for confounders, patients with baseline HbA levels =8.5% (=69 mmol/mol) had increased mortality (7 studies; HR, 1.14; 95% CI, 1.09-1.19) compared with patients with HbA levels of 6.5%-7.4% (48-57 mmol/mol). Likewise, patients with a mean HbA value =8.5% also had a higher adjusted risk of mortality (6 studies; HR,1.29; 95% CI, 1.23-1.35). There was a small but nonsignificant increase in mortality associated with mean HbA levels =5.4% (=36 mmol/mol; 6 studies; HR, 1.09; 95% CI, 0.89-1.34). Sensitivity analyses in incident (=90 days of hemodialysis) and prevalent patients (>90 days of hemodialysis) showed a similar pattern. In incident patients, mean HbA levels =5.4% also were associated with increased mortality risk (4 studies; HR, 1.29; 95% CI, 1.23-1.35). 
Limitations: Observational study data and inability to adjust for diabetes type in all studies. 
Conclusions: Despite concerns about the utility of HbA measurement in hemodialysis patients, high levels (=8.5%) are associated with increased mortality risk. Very low HbA levels (=5.4%) also may be associated with increased mortality risk.