Timing of the CKD Complications: A Longitudinal Analysis.

<b>Background.</b> Complications of chronic kidney disease include endocrine and metabolic abnormalities, anaemia and a wide range of disorders of homeostasis. Our study aims to better determine the role of CKD stage on the timing of the various complications associated with renal dysfunction. <b>Methods.</b> We performed an observational study on 71 (F:M = 39:32) patients with 486 repeated measurements, recording anemia, BUN, hyperparathyroidism, hyperphosphatemia, hyperkalemia, metabolic acidosis. Data were summarized as mean and standard deviation, median and interquartile range, or absolute number. Differences among groups were tested through the Mann-Whitney test or Pearson's Chi-Square. The associations between eGFR and each outcome was tested by Spearman's correlation test. All variables related to the outcomes (with p-value <0.1) were included in the multivariate models. Longitudinal analysis was performed using generalized estimated equations (GEE) for binary outcome and by Linear Mixed Models for continuous variables. The ROC Curve with the Youden J index was evaluated for all binary outcomes. <b>Results.</b> Baseline analysis revealed hyperparathyroidism in 49 patients (69.1%), hyperphosphatemia in 11 patients (15.5%), hyperkalemia in 20 patients (28.6%), and mean serum urea was 78 mg/dl [IQR: 59-99]. CKD stage was related with all outcomes. Youden J index suggested an eGFR predictive value of 37 ml/min/m2 for anemia, 34 ml/min/m2 for hyperkalemia, 26 ml/min/m2 for hyperphosphatemia, and 46 ml/min/m2 for hyperparathyroidism. <b>Conclusion.</b> Based on our findings, screening tests for endocrine and metabolic complications of CKD should be initiated at the beginning of the CKD stage III. We suggest screening for hyperphosphataemia at the CKD stage IV.