Comparison of Point-of-Care Testing Methods and Laboratory Analysis for Assessing Urine Specific Gravity and pH of Children Undergoing Chemotherapy

Abstract

To reduce the risk of renal toxicity, urine specific gravity (SG) and pH (potential of hydrogen) parameters should be met before nephrotoxic chemotherapeutic agents are administered. The purpose of this study was to compare laboratory urine SG and pH values with those obtained with urine point-of-care (POC) testing methods commonly used when caring for children receiving nephrotoxic chemotherapeutic agents. A method-comparison design was used to compare the values of three POC methods for SG (dipstick, automated dipstick reader, refractometer) and three pH (dipstick, automated dipstick reader, litmus paper) methods with laboratory analysis of 86 urine samples from 43 children hospitalized on a pediatric hematology oncology unit in a large academic medical center. The Bland-Altman method was used to calculate bias and precision between POC and laboratory values. Except for the SG refractometer, bias values from Bland-Altman graphs demonstrated poor agreement between POC and laboratory urine SG and pH results. The precision values between these methods indicated overestimation or underestimation of hydration or urine pH status. Compared with laboratory methods, 31% of POC visual reading of dipstick SG values were falsely low-putting the patient at risk of not receiving necessary hydration and subsequent nephrotoxicity. In conclusion, most POC urine testing methods for SG and pH are not accurate compared with laboratory analysis. Because laboratory analyses can take longer than POC methods to obtain results, clinicians need to collaborate with laboratory medicine to ensure that an expedited process is in place in order to prevent chemotherapy administration delays.