Division of Urology, Department of Surgery, University of California San Diego, San Diego, CA, USA.
Department of Urology, University of California Los Angeles, Los Angeles, CA, USA.
Investig Clin Urol. 2017 Sep;58(5):378-382. doi: 10.4111/icu.2017.58.5.378. Epub 2017 Jul 24.
Accurate measurement of pH is necessary to guide medical management of nephrolithiasis. Urinary dipsticks offer a convenient method to measure pH, but prior studies have only assessed the accuracy of a single, spot dipstick. Given the known diurnal variation in pH, a single dipstick pH is unlikely to reflect the average daily urinary pH. Our goal was to determine whether multiple dipstick pH readings would be reliably comparable to pH from a 24-hour urine analysis.
Kidney stone patients undergoing a 24-hour urine collection were enrolled and took images of dipsticks from their first 3 voids concurrently with the 24-hour collection. Images were sent to and read by a study investigator. The individual and mean pH from the dipsticks were compared to the 24-hour urine pH and considered to be accurate if the dipstick readings were within 0.5 of the 24-hour urine pH. The Bland-Altman test of agreement was used to further compare dipstick pH relative to 24-hour urine pH.
Fifty-nine percent of patients had mean urinary pH values within 0.5 pH units of their 24-hour urine pH. Bland-Altman analysis showed a mean difference between dipstick pH and 24-hour urine pH of -0.22, with an upper limit of agreement of 1.02 (95% confidence interval [CI], 0.45-1.59) and a lower limit of agreement of -1.47 (95% CI, -2.04 to -0.90).
We concluded that urinary dipstick based pH measurement lacks the precision required to guide medical management of nephrolithiasis and physicians should use 24-hour urine analysis to base their metabolic therapy.
准确测量 pH 值对于指导肾结石的医学管理至关重要。尿液试纸提供了一种方便的 pH 值测量方法，但之前的研究仅评估了单个即时尿液试纸的准确性。鉴于 pH 值存在昼夜变化，单个尿液试纸的 pH 值不太可能反映平均每日尿液 pH 值。我们的目标是确定多次尿液试纸 pH 值读数是否与 24 小时尿液分析的 pH 值可靠可比。
正在接受 24 小时尿液收集的肾结石患者参与了研究，并在进行 24 小时尿液收集的同时拍摄了他们首次 3 次排尿的尿液试纸图像。图像被发送给并由研究调查员进行阅读。将试纸的个体和平均 pH 值与 24 小时尿液 pH 值进行比较，如果试纸读数与 24 小时尿液 pH 值相差 0.5，则认为是准确的。使用 Bland-Altman 一致性检验进一步比较试纸 pH 值与 24 小时尿液 pH 值的关系。
59%的患者的平均尿液 pH 值在其 24 小时尿液 pH 值的 0.5 pH 单位内。Bland-Altman 分析显示，试纸 pH 值与 24 小时尿液 pH 值的平均差值为-0.22，一致性上限为 1.02（95%置信区间[CI]，0.45-1.59），一致性下限为-1.47（95%CI，-2.04 至-0.90）。
我们得出结论，基于尿液试纸的 pH 值测量缺乏指导肾结石医学管理所需的精度，医生应使用 24 小时尿液分析来为他们的代谢治疗提供依据。
