ABSTRACT
BACKGROUND: It has been suggested that for the accurate measurement of calcium in urine, samples must be collected into bottles containing acid. Acidification poses risks to both patients and laboratory staff. Here we reappraise whether acidification is a preanalytical necessity. METHODS: Twenty-four-hour urine samples were collected from 133 patients into bottles without acid or preservatives. In a subset of 29 patients, 10 mL aliquots were prepared to test the effect on urine calcium of 0.1, 1.0 and 5.0 mol/L hydrochloric acid (HCl). Calcium was then measured immediately after acidification, after 12 h and seven days storage at 4 degrees C. In a separate study, urine calcium concentrations in paired control (non-acidified) and acidified (with 5 mol/L HCl) samples were compared in 133 patients. When available, we recorded the time from start of urine collection to time of analysis. Calcium was measured using the cresolphthalein complexone colorimetric endpoint assay on the Roche Modular system. RESULTS: There was no significant difference in the calcium concentration in the 29 cases studied between the varying acid concentrations tested compared with non-acidified urine (P = 0.987). Overall, in 133 patients there was no difference between control and acidified samples (P = 0.888). We found no correlation between basal urine pH and urine calcium at all time points studied. CONCLUSIONS: Our results suggest that the acidification of urine samples is not a preanalytical necessity for the measurement of urine calcium.
Subject(s)
Acids/urine , Calcium/urine , Urinalysis/methods , Chemistry, Clinical/methods , Chemistry, Clinical/standards , Dose-Response Relationship, Drug , Humans , Hydrochloric Acid/chemistry , Hydrogen-Ion Concentration , Predictive Value of Tests , Reproducibility of Results , Temperature , Time FactorsABSTRACT
In the absence of pre-extraction records, the positioning of teeth on complete dentures is a somewhat arbitrary procedure. The present study was designed to evaluate a number of different criteria for tooth placement. Miniature foil strain gauges were used to measure the forces brought to bear on complete dentures by the lingual and peri-oral musculature. Previous studies of the pattern of post-extraction resorption found that the vestige of the lingual gingival margins of the maxillary teeth could be identified on the cast and it was suggested that these biometric guides are reliable for the correct placement of the upper artificial teeth. The results reported confirmed the use of biometric guides to tooth placement as a reliable method of positioning the teeth in Class I edentulous cases.
