Impact of pH on Urine Chemistry Assayed on Roche Analyzers.

BACKGROUND: The pH may impact the concentration of certain urinary parameters, making urine pre-treatment questionable.

METHODS: 1) Determining the impact of pH in vitro on the urinary concentration of chemistry parameters assayed on Roche Modular analyzers. 2) Evaluating whether concentrations depended on pH in non-pretreated urines from patients.

RESULTS: 1) The optimal urinary pH values for each measurement were: 6.3 ± 0.8 (amylase), < 5.5 (calcium and magnesium), < 6.5 (phosphorus), > 6.5 (uric acid). Urinary creatinine, sodium and urea concentrations were not pH-dependent. 2) In urines from patients, the pH was negatively associated with the concentration of some urinary parameters. However, concentrations of all the parameters were strongly and positively correlated with urinary creatinine, and relationships with pH were no longer evidenced after creatinine-normalization.

CONCLUSIONS: The need for urine pH adjustment does not seem necessary when considering renal function. However, from an analytical and accreditation standpoint, the relationship between urine pH and several parameters justifies its measurement.