Problems in the metabolic evaluation of renal stone disease: audit of intra-individual variation in urine metabolites.

Preliminary metabolic assessment of patients with renal stones includes measurement of urine metabolites. This paper reports on the degree of intra-individual variation in some key urine metabolites. Over 80 medically untreated patients under initial metabolic investigation were audited from whom 24-h urine results were available as three separate urine pairs collected at intervals not less than 1 month apart. Ranking patients by intra-individual variation, above the 75th centile, the highest calcium was at least 216% of the lowest calcium, the respective figures for phosphate, urate, oxalate, citrate, creatinine and sodium were 207, 190, 271, 412, 175 and 233%. In order to estimate pre-treatment excretion within 30% of a true mean at the 95% confidence limit, for calcium and oxalate, the number of 24-h samples required were 3 and 4 respectively with 6 and 9 required to be within 20%. These observations illustrate significant practical clinical problems in assessing patients with renal stones when assessing these basic parameters. Regimens based on small numbers of urine collections are flawed, hence evidence based protocols should be devised. A minimum of three pairs of 24-h urine samples based upon predicting metabolite output within 20-30% or less of the true mean is recommended.

Folate supplementation reduces serum hsp70 levels in patients with type 2 diabetes.

Type 2 diabetes patients are subject to oxidative stress as a result of hyperglycemia. The aim of this study was to determine whether administration of the antioxidant folic acid, previously shown to reduce homocysteine levels, would reduce circulating levels of Hsp70 while improving the condition of type 2 diabetes patients with microalbuminuria. Plasma homocysteine fell from pretreatment values of 12.9 to 10.3 microM (P < 0.0001). The urine albumin-creatinine ratio fell from 12.4 to 10.4 mg/mM (P = 0.38). Pretreatment Hsp70 levels were higher in patients not taking insulin (5.32 ng/mL) compared with those on insulin (2.44 ng/mL) (P = 0.012). Folic acid supplementation resulted in a significant fall in Hsp70 (5.32 to 2.05 ng/mL) (P = 0.004). There was no change in Hsp70 in those receiving insulin. Folic acid supplementation in non-insulin-treated type 2 diabetes patients, therefore, resulted in a fall in Hsp70, reflecting an improvement in oxidative stress. The data shows that improvement in homocysteine status can lead to a reduction in Hsp70, indicating the possibility of its use as a marker for severity of disease.