A UK & Ireland national audit of urine acidification.

Objective To evaluate the spot urine sample collection method and value of urinary albumin measurement in population survey. Methods Six hundred and fifty-nine Beijing residents were requested to collect 24 h urine for detection of UAER, as well as random spot urine samples and morning urine samples in the next day. Rapid semi-quantitative urinary albumin-specific dipstick and ACR were measured in each spot urine specimen. The 24 h UAER was measured as golden standard to generate ROC curves and evaluate the sensitivity, specificity and AUC of each method. Results The value of ACR in the morning spot urine samples and random spot urine samples were 9. 36(5. 12-33.29) mg/g and 11.29(6. 34-41.29) mg/g respectively and there was no significant difference between these two groups (t = - 1. 382,P＞0.05). The correlation was significant in the two groups (r = 0.932, P ＜ 0.01). The correlation coefficient between ACR in the morning spot urine samples and UAER was 0. 853 (P ＜ 0. 01). The correlation coefficient between ACR in the random spot urine samples and UAER was 0. 874 (P ＜0. 01).The sensitivity and specificity of ACR for diagnosis of albuminuria in the random urine samples were 77. 9% and 91.0%. The sensitivity and specificity of ACR for diagnosis of albuminuria in the morning urine samples were 78. 4% and 95.7%. Concerning the semi-quantitative urinary albumin-specific dipstick, sensitivity and specificity were 90. 3% and 41.1% , respectively. The specificity was much lower than that of ACR. The area under the ROC curves of ACR in the random urine specimens and the morning urine specimens was 0. 918 ±0. 012, 0. 929 ± 0. 015, respectively. There was no statistical difference between these two groups (χ2 =2. 13, P＞0. 05). The area under the ROC curves of semi-quantitative urinary albumin-specific dipstick in the random urine specimens was 0.661 ±0.021, lower than that of ACR (χ2 = 248.41, P＜0.01).Conclusion Measurement of ACR in random urine samples is a reasonable method with simplicity and accuracy for the detection of albuminuria in general population screening program. Key words: Albuminuria; Urinalysis Albumins; Creatinine; Kidney failure,chronic; Epidemiological studies

Assessment of Proteinuria

Objectives: The high incidence of invasive cervical cancer among those who have not undergone cancer screening is a serious problem. This study aimed to investigate the utility of human papillomavirus (HPV) test results from self-collected urine and vaginal samples as screening tools. Design: The study was conducted in two steps. First, the appropriate storage container, temperature, and time until urine HPV assay performance were verified. Second, the results of spot urine testing under those conditions and of gynecologist-collected cervical and self-collected vaginal samples were compared to verify the feasibility of using the BD Onclarity® HPV assay for individuals with abnormal cervical cytology. Participants/Materials, Setting, Methods: The participants were 121 women with abnormal cervical cytology. Self-collected urine and vaginal samples, along with gynecologist-collected cervical samples, were tested for HPV using the BD Onclarity® HPV assay. The optimal conditions for urine sample storage were identified by comparing the HPV detection rates under various conditions. Results: Urine stored in a BD Probe Tec™ (QxUPT) for less than 72 h at room temperature was found to have the highest HPV positivity rate. Under these conditions, the detection rates of HPV in urine, cervical, and vaginal samples were examined. HPV type 16 was detected in 41.7% of the cervical samples, type 18 in 10%, and types 31 and 52 in 12.6% each. The concordance rate for HPV testing between clinician-collected cervical and urine samples was 63.9% (kappa: 0.34; 95% CI: 0.21–0.47), and that between clinician-collected cervical and self-collected vaginal samples was 77.8% (kappa: 0.68; 95% CI: 0.53–0.83), indicating good concordance. In a population with an HPV-related lesion/tumor prevalence of approximately 70%, the sensitivity of HPV testing was 82.7% for the cervix, 46.4% for urine, and 75.7% for vaginal samples. Limitations: The primary limitation is the lower detection rate of HPV in spot urine samples than in other sample types, indicating room for methodological improvement. The study’s findings are based on a specific population, which may limit generalizability. Conclusions: We investigated the optimal self-collected urine-to-testing time and temperature. Self-collected vaginal and urine HPV tests show moderate-high concordance with clinician-collected cervical HPV tests, suggesting their potential utility for women who do not undergo regular cancer screening. However, the sensitivity was not high in spot urine. Therefore, further large-scale studies are needed to verify these findings and optimize testing methods to encourage broader participation in cancer screening programs. Objectives: The high incidence of invasive cervical cancer among those who have not undergone cancer screening is a serious problem. This study aimed to investigate the utility of human papillomavirus (HPV) test results from self-collected urine and vaginal samples as screening tools. Design: The study was conducted in two steps. First, the appropriate storage container, temperature, and time until urine HPV assay performance were verified. Second, the results of spot urine testing under those conditions and of gynecologist-collected cervical and self-collected vaginal samples were compared to verify the feasibility of using the BD Onclarity® HPV assay for individuals with abnormal cervical cytology. Participants/Materials, Setting, Methods: The participants were 121 women with abnormal cervical cytology. Self-collected urine and vaginal samples, along with gynecologist-collected cervical samples, were tested for HPV using the BD Onclarity® HPV assay. The optimal conditions for urine sample storage were identified by comparing the HPV detection rates under various conditions. Results: Urine stored in a BD Probe Tec™ (QxUPT) for less than 72 h at room temperature was found to have the highest HPV positivity rate. Under these conditions, the detection rates of HPV in urine, cervical, and vaginal samples were examined. HPV type 16 was detected in 41.7% of the cervical samples, type 18 in 10%, and types 31 and 52 in 12.6% each. The concordance rate for HPV testing between clinician-collected cervical and urine samples was 63.9% (kappa: 0.34; 95% CI: 0.21–0.47), and that between clinician-collected cervical and self-collected vaginal samples was 77.8% (kappa: 0.68; 95% CI: 0.53–0.83), indicating good concordance. In a population with an HPV-related lesion/tumor prevalence of approximately 70%, the sensitivity of HPV testing was 82.7% for the cervix, 46.4% for urine, and 75.7% for vaginal samples. Limitations: The primary limitation is the lower detection rate of HPV in spot urine samples than in other sample types, indicating room for methodological improvement. The study’s findings are based on a specific population, which may limit generalizability. Conclusions: We investigated the optimal self-collected urine-to-testing time and temperature. Self-collected vaginal and urine HPV tests show moderate-high concordance with clinician-collected cervical HPV tests, suggesting their potential utility for women who do not undergo regular cancer screening. However, the sensitivity was not high in spot urine. Therefore, further large-scale studies are needed to verify these findings and optimize testing methods to encourage broader participation in cancer screening programs.

Metabolic evaluation of stone-forming (SF) patients is based on the determination of calcium, oxalate, citrate, uric acid and other parameters in 24-h urine samples under a random diet. A reliable measurement of urinary oxalate requires the collection of urine in a receptacle containing acid preservative. However, urinary uric acid cannot be determined in the same sample under this condition. Therefore, we tested the hypothesis that the addition of preservatives (acid or alkali) after urine collection would not modify the results of those lithogenic parameters. Thirty-four healthy subjects (HS) were submitted to two non-consecutive collections of 24-h urine. The first sample was collected in a receptacle containing hydrochloric acid (HCl 6 N) and the second in a dry plastic container, with HCl being added as soon as the urine sample was received at the laboratory. Additionally, 34 HS and 34 SF patients collected a spot urine sample that was divided into four aliquots, one containing HCl, another containing sodium bicarbonate (NaHCO(3 )5 g/l), and two others in which these two preservative agents were added 24 h later. Urinary oxalate, calcium, magnesium, citrate, creatinine and uric acid were determined. Urinary parameters were also evaluated in the presence of calcium oxalate or uric acid crystals. Mean values of all urinary parameters obtained from previously acidified 24-h urine samples did not differ from those where acid was added after urine collection. The same was true for spot urine samples, with the exception of urinary citrate that presented a slight albeit significant change of 5.9% between samples in HS and 3.1% in SF. Uric acid was also not different between pre- and post-alkalinized spot urine samples. The presence of crystals did not alter these results. We concluded that post-delivery acidification or alkalinization of urine samples does not modify the measured levels of urinary oxalate, calcium, magnesium, creatinine and uric acid, and that the change on citrate was not relevant, hence allowing all parameters to be determined in a single urine sample, thus avoiding the inconvenience and cost of multiple 24-h urine sample collections.

Spot and Cumulative Urine Samples Are Suitable Replacements for 24-Hour Urine Collections for Objective Measures of Dietary Exposure in Adults Using Metabolite Biomarkers

Calcium lithiasis is the most frequently diagnosed renal lithiasis and is associated with a high percentage of patients with metabolic disorders, such as hypercalciuria, hypocitraturia, and hyperoxaluria. The present study included 50 patients with recurrent calcium lithiasis. We conducted a random urine test during nocturnal fasting and a 24-h urine test, and examined calcium, oxalate, and citrate. A study of the linear correlation between the metabolites was performed, and the receiver operator characteristic (ROC) curves were analyzed in the random urine samples to determine the cutoff values for hypercalciuria (excretion greater than 200 mg), hyperoxaluria (excretion greater than 40 mg), and hypocitraturia (excretion less than 320 mg) in the 24-h urine. Linear relationships were observed between the calcium levels in the random and 24-h urine samples (R = 0.717, p = 0.0001), the oxalate levels in the random and 24-h urine samples (R = 0.838, p = 0.0001), and the citrate levels in the random and 24-h urine samples (R = 0.799, p = 0.0001). After obtaining the ROC curves, we observed that more than 10.15 mg/dl of random calcium and more than 16.45 mg/l of random oxalate were indicative of hypercalciuria and hyperoxaluria, respectively, in the 24-h urine. In addition, we found that the presence of less than 183 mg/l of random citrate was indicative of the presence of hypocitraturia in the 24-h urine. Using the proposed values, screening for hypercalciuria, hyperoxaluria, and hypocitraturia can be performed with a random urine sample during fasting with an overall sensitivity greater than 86%.

Estimating equations based on spot urine samples have been identified as a possible alternative approach to 24-h urine collections for determining mean population salt intake. This review compares estimates of mean population salt intake based upon spot and 24-h urine samples. We systematically searched for all studies that reported estimates of daily salt intake based upon both spot and 24-h urine samples for the same population. The associations between the two were quantified and compared overall and in subsets of studies. A total of 538 records were identified, 108 were assessed as full text and 29 were included. The included studies involved 10,414 participants from 34 countries and made 71 comparisons available for the primary analysis. Overall average population salt intake estimated from 24-h urine samples was 9.3 g/day compared with 9.0 g/day estimated from the spot urine samples. Estimates based upon spot urine samples had excellent sensitivity (97%) and specificity (100%) at classifying mean population salt intake as above or below the World Health Organization maximum target of 5 g/day. Compared with the 24-h samples, estimates based upon spot urine overestimated intake at lower levels of consumption and underestimated intake at higher levels of consumption. Estimates of mean population salt intake based upon spot urine samples can provide countries with a good indication of mean population salt intake and whether action on salt consumption is required.

While daily hydration is best assessed in a 24-h urine sample, using a urine spot sample can be more practical for healthcare professionals, researchers, and individuals. Although urine product is subject to circadian variation, 24-h urine concentration reported to be approximated from a mid- to late-afternoon spot urine sample in adults. However, no data exists in children. PURPOSE: To identify time windows during which spot values of urine osmolality (UOsm) is representative of 24-h values in healthy children. METHODS: Among 541 healthy children (age: 3-13 y, female: 45%, BMI: 17.7±4.0 kg∙m-2), equivalent test was performed by comparing UOsm from specific time windows [morning (0600-1159), early afternoon (1200-1559), late afternoon (1600-1959), evening (2000-2359), overnight (2400-0559), and first morning (0600-0959)] to 24-h urine sample. The equivalency was determined when the mean difference and the confident interval between the spot and 24-h urine sample fell below the bound of 80 mmol·kg-1. The analysis was performed by using the first spot urine sample from each time window. Other spot urine samples after the first spot urine within each time window were not used to avoid unequally weighting data. RESULTS: Equivalence test showed that the late afternoon (1600-1959) spot urine sample UOsm value was equivalent to the 24-h UOsm value in children (P<0.05; mean difference: 62; CI: 45-78). The overall diagnostic ability of urine osmolality assessed at late afternoon (1600-1959) to diagnose elevated urine osmolality (>800 mmol·kg-1) on the 24-h sample was "good" (area under the curve: 87.4%; sensitivity: 72.6%; specificity: 90.5%; threshold: 814 mmol·kg-1). CONCLUSIONS: These data suggest that in free-living healthy children, 24-h urine concentration can be approximated from a late afternoon spot urine sample.

The objectives of this study were to recruit agricultural workers in Costa Rica to participate in a 24-hour urine collection for paraquat exposure assessment and to compare the 24-hour sampling to end-of-shift sampling. The authors recruited 187 handlers and 54 nonhandlers from coffee, banana, and palm oil plantations. The completeness of 24-hour urine samples collected (a total of 393 samples) was confirmed by questionnaire and urinary creatinine level. For a subset of 12 samples, the absorbed paraquat level was determined in 24-hours and end-of-shift spot urine samples. The participation rate for handlers was ∼90%. The completeness of 24-hour urine collections was verified as the overall average of creatinine levels from 393 urines (1.11 ± 0.50 g/L). A total of 92.4% to 96.7% of urine samples were considered within the acceptable range of urinary creatinine, whereas 94.7% of the samples were described as “complete” from the questionnaire. Measured creatinine correlated well to predicted values (r = .327, p = .0024, 95% CI .12–.51). Detected paraquat levels in spot urine samples had a sensitivity of 96.9% at the high specificity of 100% compared to 24-hour urine samples as the gold standard. There was a significant (p < .0001) correlation between spot and 24-hour urine paraquat levels (r = .7825, 95% CI .61–.88). The recruiting strategy was successful in getting 24-hour urine samples from a farm worker population. Comparison between the paraquat levels in spot and 24-hour urine samples demonstrated that for this compound, end-of-shift spot urine samples would be an appropriate substitute for 24-hour collections.

Background: Dialkyl phosphate (DAP) metabolites in spot urine samples are frequently used to characterize children’s exposures to organophosphorous (OP) pesticides. However, variable exposure and short biological half-lives of OP pesticides could result in highly variable measurements, leading to exposure misclassification. Objective: We examined within- and between-child variability in DAP metabolites in urine samples collected during 1 week. Methods: We collected spot urine samples over 7 consecutive days from 25 children (3–6 years of age). On two of the days, we collected 24-hr voids. We assessed the reproducibility of urinary DAP metabolite concentrations and evaluated the sensitivity and specificity of spot urine samples as predictors of high (top 20%) or elevated (top 40%) weekly average DAP metabolite concentrations. Results: Within-child variance exceeded between-child variance by a factor of two to eight, depending on metabolite grouping. Although total DAP concentrations in single spot urine samples were moderately to strongly associated with concentrations in same-day 24-hr samples (r ? 0.6–0.8, p &lt; 0.01), concentrations in spot samples collected &gt; 1 day apart and in 24-hr samples collected 3 days apart were weakly correlated (r ? –0.21 to 0.38). Single spot samples predicted high (top 20%) and elevated (top 40%) full-week average total DAP excretion with only moderate sensitivity (? 0.52 and ? 0.67, respectively) but relatively high specificity (? 0.88 and ? 0.78, respectively). Conclusions: The high variability we observed in children’s DAP metabolite concentrations suggests that single-day urine samples provide only a brief snapshot of exposure. Sensitivity analyses suggest that classification of cumulative OP exposure based on spot samples is prone to type 2 classification errors.

Background: Dialkyl phosphate (DAP) metabolites in spot urine samples are frequently used to characterize children’s exposures to organophosphorous (OP) pesticides. However, variable exposure and short biological half-lives of OP pesticides could result in highly variable measurements, leading to exposure misclassification.Objective: We examined within- and between-child variability in DAP metabolites in urine samples collected during 1 week.Methods: We collected spot urine samples over 7 consecutive days from 25 children (3–6 years of age). On two of the days, we collected 24-hr voids. We assessed the reproducibility of urinary DAP metabolite concentrations and evaluated the sensitivity and specificity of spot urine samples as predictors of high (top 20%) or elevated (top 40%) weekly average DAP metabolite concentrations.Results: Within-child variance exceeded between-child variance by a factor of two to eight, depending on metabolite grouping. Although total DAP concentrations in single spot urine samples were moderately to strongly associated with concentrations in same-day 24-hr samples (r ≈ 0.6–0.8, p < 0.01), concentrations in spot samples collected > 1 day apart and in 24-hr samples collected 3 days apart were weakly correlated (r ≈ –0.21 to 0.38). Single spot samples predicted high (top 20%) and elevated (top 40%) full-week average total DAP excretion with only moderate sensitivity (≈ 0.52 and ≈ 0.67, respectively) but relatively high specificity (≈ 0.88 and ≈ 0.78, respectively).Conclusions: The high variability we observed in children’s DAP metabolite concentrations suggests that single-day urine samples provide only a brief snapshot of exposure. Sensitivity analyses suggest that classification of cumulative OP exposure based on spot samples is prone to type 2 classification errors.

Spot urine samples are easier to collect than 24-h urine samples and have been used with estimating equations to derive the mean daily salt intake of a population. Whether equations using data from spot urine samples can also be used to estimate change in mean daily population salt intake over time is unknown. We compared estimates of change in mean daily population salt intake based upon 24-h urine collections with estimates derived using equations based on spot urine samples. Paired and unpaired 24-h urine samples and spot urine samples were collected from individuals in two Australian populations, in 2011 and 2014. Estimates of change in daily mean population salt intake between 2011 and 2014 were obtained directly from the 24-h urine samples and by applying established estimating equations (Kawasaki, Tanaka, Mage, Toft, INTERSALT) to the data from spot urine samples. Differences between 2011 and 2014 were calculated using mixed models. A total of 1000 participants provided a 24-h urine sample and a spot urine sample in 2011, and 1012 did so in 2014 (paired samples n = 870; unpaired samples n = 1142). The participants were community-dwelling individuals living in the State of Victoria or the town of Lithgow in the State of New South Wales, Australia, with a mean age of 55 years in 2011. The mean (95% confidence interval) difference in population salt intake between 2011 and 2014 determined from the 24-h urine samples was -0.48g/day (-0.74 to -0.21; P < 0.001). The corresponding result estimated from the spot urine samples was -0.24 g/day (-0.42 to -0.06; P = 0.01) using the Tanaka equation, -0.42 g/day (-0.70 to -0.13; p = 0.004) using the Kawasaki equation, -0.51 g/day (-1.00 to -0.01; P = 0.046) using the Mage equation, -0.26 g/day (-0.42 to -0.10; P = 0.001) using the Toft equation, -0.20 g/day (-0.32 to -0.09; P = 0.001) using the INTERSALT equation and -0.27 g/day (-0.39 to -0.15; P < 0.001) using the INTERSALT equation with potassium. There was no evidence that the changes detected by the 24-h collections and estimating equations were different (all P > 0.058). Separate analysis of the unpaired and paired data showed that detection of change by the estimating equations was observed only in the paired data. All the estimating equations based upon spot urine samples identified a similar change in daily salt intake to that detected by the 24-h urine samples. Methods based upon spot urine samples may provide an approach to measuring change in mean population salt intake, although further investigation in larger and more diverse population groups is required.

Short term temporal variability of selected organophosphate esters among healthy adults living in the National Capital Region of Canada

To assess whether urine protein-to-creatinine (UPC) ratios determined in urine samples collected by cystocentesis versus those collected by free catch provide similar diagnostic information for dogs. Evaluation study. 115 client-owned dogs evaluated because of various health problems requiring urinalysis or to screen for proteinuria in an area endemic for leishmaniasis. 230 paired urine samples, 1 collected by cystocentesis and 1 by free catch, were collected from the 115 dogs. The UPC ratio was determined in paired urine samples (n = 162) from 81 dogs with no indication of active inflammation according to urine sediment analysis. On the basis of the UPC ratio of urine sample collected by cystocentesis, dogs were classified as nonproteinuric (UPC ratio < 0.2), borderline proteinuric (UPC ratio of 0.2 to 0.5), or proteinuric (UPC ratio > 0.5), according to the International Renal Interest Society (IRIS). The correlation between UPC ratio in urine samples collected by cystocentesis and by free catch was strong (r(2) = 0.90); 75 of 81 (92.6%) dogs had UPC ratios from both urine samples that resulted in classification in the same IRIS substage with a kappa coefficient of 0.83. The UPC ratio in dogs was minimally affected in urine samples collected by free catch, thus allowing correct grading of proteinuria with this method. The high reliability of the UPC ratio in free-catch urine samples coupled with the ease of collection should increase the use of this value for assessment of proteinuria.

Preterm infants have physiological proteinuria and values of urine protein to creatinine ratio (UPr/Cr) are higher compared to full-term infants during the first week of life. Few investigations explored the changes of proteinuria in very preterm infants (VPI, ≤ 31weeks of gestation) older than a week, and it is unclear whether high and persistent proteinuria is associated with kidney injury in this population. This study aimed to (1) observe the changes of UPr/Cr during the first month of life in VPI and (2) describe clinical and biological variables associated with the changes of UPr/Cr. Spot urine samples for UPr/Cr were collected on the first day of life (DOL1) and then on DOL2-3, DOL5-6, second week of life (WOL2), WOL3, and WOL4 in VPI cared for in a third-level NICU. We tested the relationship of UPr/Cr with perinatal variables and diseases. A total of 1140 urine samples were obtained for 190 infants. UPr/Cr values (mg/mmol) (median with interquartile) at DOL1, DOL2, DOL3, WOL2, WOL3, and WOL4 were, respectively, 191 (114-399), 226 (152-319), 225 (156-350), 282 (200-488), 308 (188-576), and 325 (175-664). At the multivariate analysis, lower gestational age (GA) and increasing postnatal age were the only variables significantly associated with higher UPr/Cr values (p < 0.001). There was wide intra- and interindividual variability in UPr/Cr, especially in infants with higher GA and clinical stability. In VPI, UPr/Cr is higher at lower GA and increases with advancing postnatal age. High persistent proteinuria is not associated with clinical and biological variables reflecting kidney injury during the first month of life. A higher resolution version of the Graphical abstract is available as Supplementary information.