Do over-the-counter digital pH meters maintain accuracy over time for patient home pH urine monitoring?
BAUS ePoster online library. Smith A. 06/21/21; 319103; p6-5
Disclosure(s): Travere; Boston Scientific, Advicenne
Alice Smith
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Abstract
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Introduction:We previously found over-the-counter digital pH meters(OTCM) were more accurate than pH strips but required regular calibration. We now assess different OTCM that patients might purchase for home testing to assess if they maintain accuracy following calibration.
Methods:We selected 4 digital pH meters that were available online at varying costs(£10-£100). The accuracy was compared with those of a gold-standard laboratory meter(GSLM). All were used weekly for four weeks on 20 fresh clinic urine samples. OTCM were calibrated once at the start of the project; The GSLM was calibrated before each use. Student's t-test and linear regression analysis was performed.
Results:OTCM were significantly less accurate than the GSLM and develop alkaline bias over time. All OTCM showed significant initial negative bias (largest -0.26(p=0.0003)). No significance was found in week 2, as the mean readings crossed the zero-difference threshold. By week 4 mean readings of all OTCM's had become significantly more alkaline than the mean GSLM readings with the most positive error +0.34(p=1.9×10^(-11)). Positive correlations were identified when readings were stratified into acidic/neutral/alkaline urines, suggesting that the accuracy of OTCM may be dependent on the pH range they are measuring.
Conclusion:OTCM demonstrate consistent and statistically significant differences which changes over time from calibration. Patients and clinicians should be aware of these differences although as most reagent strips only measure to +/-0.5, OTCM still offer better accuracy and removes the subjective judgement of colour from reagent strips. Our study suggests that calibration can be deferred to a minimum of every 4 weeks.
Methods:We selected 4 digital pH meters that were available online at varying costs(£10-£100). The accuracy was compared with those of a gold-standard laboratory meter(GSLM). All were used weekly for four weeks on 20 fresh clinic urine samples. OTCM were calibrated once at the start of the project; The GSLM was calibrated before each use. Student's t-test and linear regression analysis was performed.
Results:OTCM were significantly less accurate than the GSLM and develop alkaline bias over time. All OTCM showed significant initial negative bias (largest -0.26(p=0.0003)). No significance was found in week 2, as the mean readings crossed the zero-difference threshold. By week 4 mean readings of all OTCM's had become significantly more alkaline than the mean GSLM readings with the most positive error +0.34(p=1.9×10^(-11)). Positive correlations were identified when readings were stratified into acidic/neutral/alkaline urines, suggesting that the accuracy of OTCM may be dependent on the pH range they are measuring.
Conclusion:OTCM demonstrate consistent and statistically significant differences which changes over time from calibration. Patients and clinicians should be aware of these differences although as most reagent strips only measure to +/-0.5, OTCM still offer better accuracy and removes the subjective judgement of colour from reagent strips. Our study suggests that calibration can be deferred to a minimum of every 4 weeks.
Introduction:We previously found over-the-counter digital pH meters(OTCM) were more accurate than pH strips but required regular calibration. We now assess different OTCM that patients might purchase for home testing to assess if they maintain accuracy following calibration.
Methods:We selected 4 digital pH meters that were available online at varying costs(£10-£100). The accuracy was compared with those of a gold-standard laboratory meter(GSLM). All were used weekly for four weeks on 20 fresh clinic urine samples. OTCM were calibrated once at the start of the project; The GSLM was calibrated before each use. Student's t-test and linear regression analysis was performed.
Results:OTCM were significantly less accurate than the GSLM and develop alkaline bias over time. All OTCM showed significant initial negative bias (largest -0.26(p=0.0003)). No significance was found in week 2, as the mean readings crossed the zero-difference threshold. By week 4 mean readings of all OTCM's had become significantly more alkaline than the mean GSLM readings with the most positive error +0.34(p=1.9×10^(-11)). Positive correlations were identified when readings were stratified into acidic/neutral/alkaline urines, suggesting that the accuracy of OTCM may be dependent on the pH range they are measuring.
Conclusion:OTCM demonstrate consistent and statistically significant differences which changes over time from calibration. Patients and clinicians should be aware of these differences although as most reagent strips only measure to +/-0.5, OTCM still offer better accuracy and removes the subjective judgement of colour from reagent strips. Our study suggests that calibration can be deferred to a minimum of every 4 weeks.
Methods:We selected 4 digital pH meters that were available online at varying costs(£10-£100). The accuracy was compared with those of a gold-standard laboratory meter(GSLM). All were used weekly for four weeks on 20 fresh clinic urine samples. OTCM were calibrated once at the start of the project; The GSLM was calibrated before each use. Student's t-test and linear regression analysis was performed.
Results:OTCM were significantly less accurate than the GSLM and develop alkaline bias over time. All OTCM showed significant initial negative bias (largest -0.26(p=0.0003)). No significance was found in week 2, as the mean readings crossed the zero-difference threshold. By week 4 mean readings of all OTCM's had become significantly more alkaline than the mean GSLM readings with the most positive error +0.34(p=1.9×10^(-11)). Positive correlations were identified when readings were stratified into acidic/neutral/alkaline urines, suggesting that the accuracy of OTCM may be dependent on the pH range they are measuring.
Conclusion:OTCM demonstrate consistent and statistically significant differences which changes over time from calibration. Patients and clinicians should be aware of these differences although as most reagent strips only measure to +/-0.5, OTCM still offer better accuracy and removes the subjective judgement of colour from reagent strips. Our study suggests that calibration can be deferred to a minimum of every 4 weeks.
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