OBJECTIVES: To assess (i) the extent to which urinary supersaturation (SS) has successfully discriminated between stone formers (SF) and healthy individuals (N), (ii) whether absolute SS has diagnostic worth and (iii) whether high SS is the fundamental cause of stone formation per se.
MATERIALS AND METHODS: Google Scholar was used to identify studies in which urinary compositional data had been determined. In those cases where SS values were not given, or where other risk indices had been reported, they were (re-)calculated. Collected data were termed "global" but were then "filtered" according to stone type and protocols used for SS calculations. SS distribution plots for calcium oxalate, brushite and uric acid were constructed. Data were statistically analysed using the unpaired t and Mann-Whitney tests.
RESULTS: A total of 47 studies yielded 123 SS values for N and 122 values for SF. Mean and median SS values were significantly greater in SF compared to N in all but one of the comparisons. Wide variations in SS occurred for N and SF. The two groups could not be separated.
CONCLUSIONS: Absolute SS has no diagnostic worth. It is impossible to quantify the meaning of a "high" SS value. Urines cannot be identified as originating from N or SF based on their SS. Supersaturation should be determined in clinical and research settings for relative comparisons during the assessment of treatment efficacies. This study provides a compelling argument for SS being a casual factor rather than a causal one.
Written by:
Rodgers AL. Are you the author?
Department of Chemistry, University of Cape Town, South Africa.
Reference: BJU Int. 2013 Oct 4. Epub ahead of print.
doi: 10.1111/bju.12481
PubMed Abstract
PMID: 24119074
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