Systematic review of the evidence underlying the association between mineral metabolism disturbances and risk of fracture and need for parathyroidectomy in CKD.

BACKGROUND: Chronic kidney disease (CKD) is associated with such complications as fractures and the need for parathyroidectomy. Mineral metabolism control in patients with CKD has been poor. Studies have assessed fractures and parathyroidectomy risk with mineral disturbances, but with considerable diversity in methods. Thus, a systematic review was conducted to assess method or clinical heterogeneity by comparing the design, analytical techniques, and results of studies. STUDY DESIGN: Systematic review of the MEDLINE, EMBASE, and Cochrane databases between 1980 and December 2007. SETTING & POPULATION: Patients with CKD or dialysis patients. SELECTION CRITERIA FOR STUDIES: Observational and clinical trials investigating the risk of fractures or parathyroidectomy with mineral disturbances. PREDICTOR: Mineral metabolism variables (phosphorus, calcium, and parathyroid hormone [PTH] levels). OUTCOMES: Fractures, need for parathyroidectomy. RESULTS: 9 studies were identified that assessed fractures (n = 6) or need for parathyroidectomy (n = 3). Data for fractures or parathyroidectomy risk in predialysis patients are absent. Diversity across studies was observed in populations, methods of exposure assessment, adjusted covariates, and reference mineral levels used in risk estimation. A significant fracture risk was observed with increasing PTH levels. However, additional data are required to understand fracture risk with changes in phosphorus or calcium levels. Data supported greater parathyroidectomy risk with increasing PTH, phosphorus, or calcium levels. LIMITATIONS: Clinical and method heterogeneity across studies precluding the quantitative synthesis of data. CONCLUSIONS: Serious limitations were observed in the number, quality, and method rigor of studies. Despite heterogeneity across studies, data suggest a significant parathyroidectomy risk with mineral disturbances and a fracture risk with increasing PTH levels in dialysis patients. Additional high-quality data for risk of fractures or parathyroidectomy with changes in phosphorus, calcium, or PTH levels is required to highlight the importance of managing such common, but subclinical, conditions as mineral metabolism disturbances.

Systematic review of the evidence underlying the association between mineral metabolism disturbances and risk of all-cause mortality, cardiovascular mortality and cardiovascular events in chronic kidney disease.

BACKGROUND: Chronic kidney disease (CKD) is a powerful risk factor for all-cause mortality and its most common aetiology, cardiovascular (CV) mortality. Mineral metabolism disturbances occur very early during the course of CKD but their control has been poor. A number of studies have assessed the relationship between all-cause mortality, CV mortality and events with mineral disturbances in CKD patients, but with considerable discrepancy and heterogeneity in results. Thus, a systematic review was conducted to assess methodological and clinical heterogeneity by comparing designs, analytical approaches and results of studies. METHODS: Medline, EMBASE and Cochrane databases were systematically searched for articles published between January 1980 and December 2007. RESULTS: Thirty-five studies were included in the review. All-cause mortality was the most commonly assessed outcome (n = 29). Data on CV mortality risk (n = 11) and CV events (congestive heart failure, stroke, myocardial infarction) (n = 4) are limited. The studies varied in populations scrutinized, exposure assessments, covariates adjusted and reference mineral levels used in risk estimation. A significant risk of mortality (all-cause, CV) and of CV events was observed with mineral disturbances. The data supported a greater mortality risk with phosphorus, followed by calcium and parathyroid hormone (PTH). The threshold associated with a significant all-cause mortality risk varied from 3.5-3.9 mg/dL (reference: 2.5-2.9) to 6.6-7.8 mg/dL (reference: 4.4-5.5) for high phosphorus, <3 mg/dL (reference: 5-7) to <5 mg/dL (reference: 5-6) for low phosphorus, 9.7-10.2 mg/dL (reference: < or =8.7) to >10.5 mg/dL (reference: 9-9.5) for high calcium, < or =8.8 mg/dL (reference: >8.8) to <9 mg/dL (reference: 9-9.5) for low calcium and >300 pg/mL (reference: 200-300) to >480 pg/mL (reference: < or =37) for PTH. Thresholds at which the CV mortality risk significantly increased were >5.5 (reference: 3.5-5.5) and >6.5 mg/dL (reference: <6.5) for phosphorus and >476.1 pg/mL (reference: <476.1) for PTH. CONCLUSIONS: Serious limitations were observed in the quality and methodology across studies. In spite of enormous heterogeneity across studies, a significant mortality risk was observed with mineral disturbances in dialysis patients. Data on risk in pre-dialysis patients were less conclusive due to even more limited (numerically) evidence.