Thyroid Function Test Derangements and Mortality in Dialysis Patients: A Systematic Review and Meta-analysis

Background: We evaluated current evidence associating thyroid function test result derangements with risk for mortality in patients with chronic kidney failure treated by long-term dialysis.

Study design: Systematic review and meta-analysis of cohort studies.

Setting & population: Dialysis patients.

Selection criteria for studies: We searched PubMed, Web of Science, Science Citation Index, Cochrane Library, and Embase databases from inception through December 2015.

Predictors: Hypothyroidism (thyrotropin level greater than reference range) and low triiodothyronine (T₃) and thyroxine (T₄) levels.

Outcomes: All-cause and cardiovascular mortality.

Results: 12 studies involving 14,766 participants (4,450 deaths) were identified. Of those, 6 studies provided data for cardiovascular mortality (2,772 participants with 327 cardiovascular deaths). Overall, confidence in the available evidence was moderate. Pooled adjusted HRs for all-cause mortality associated with hypothyroidism, low T₃ level, and low T₄ level were 1.24 (95% CI, 1.14-1.34), 1.67 (95% CI, 1.23-2.27), and 2.40 (95% CI, 1.47-3.93), respectively. Pooled adjusted HRs for cardiovascular mortality associated with low T₃ and T₄ levels were 1.84 (95% CI, 1.24-2.74) and 3.06 (95% CI, 1.29-7.24), respectively.

Limitations: Fewer studies reporting on T₄ and thyrotropin outcomes.

Conclusions: In patients treated with long-term dialysis, (cardiovascular) mortality is consistently higher in the presence of thyroid function test result derangements.