Associations Between Hyponatremia, Volume Depletion, and the Risk of Falls in US Hospitalized Patients: A Case-Control Study

GENERAL COMMENTS The authors present a well designed case control study to assess the utility of lab tests suggesting hypovolemia to predict the odds of experiencing a fall in hospitalized patients. While the study has a robust statistical analysis based on good methodological design a couple of assumptions are erroneous to allow appropriate clinical interpretation of numerical data. 1. Hyponatremia may or may not be secondary to hypovolemia. This is especially so in elderly hyponatremics where the incidence of euvolemic hyponatremia such as SIADH or reset osmostat are high 2. Test characteristics of BUN, Cr or BUN/Cr ratio to define hypovolemia must be given to appropriately interpret results. The indicated references in the manuscript #10, 26-29 are not primary data but clinical reviews not clearly mentioning this assumption 3.CKD itself is a major risk for falls or fracturesadjusted analysis does not mention this 4. CHF, internal bleeding or hypercatabolic states can also elevate BUN/Cr ratio so this must be mentioned as caveats to using biochemical parameters to indicate hypovolemia 5. At the best, based on data presented, it can be said that prevalent hyponatremia and not renal dysfunction increases the odds of falls in hospitalized patients when adjusting for well known risk factors.