Multisite evaluation of a new dipstick for albumin, protein, and creatinine

Diagnostic accuracy of urine dipstick tests for proteinuria in pregnant women suspected of preeclampsia: A systematic review and meta-analysis

OBJECTIVES

Dipstick tests are frequently used as bedside proteinuria tests to evaluate women suspected of preeclampsia and may inform diagnosis in low resource settings lacking laboratory facilities. This systematic review and meta-analysis aimed to (1) estimate the diagnostic accuracy of urine dipsticks in diagnosing proteinuria, (2) compare performance of different dipstick types and (3) estimate their related costs.

METHODS

MEDLINE and EMBASE were searched up to August 1, 2020 for primary studies with cross-sectional diagnostic accuracy data on dipstick test(s) compared to a laboratory reference standard (24-hour protein ≥ 300 mg or protein-creatinine ratio ≥ 30 mg/mmol) in pregnant women ≥ 20 weeks of gestation suspected of preeclampsia. Risk of bias and applicability was assessed with QUADAS-2. Data were analysed using a bivariate model with hierarchical addition of covariates for subgroups.

RESULTS

Nineteen studies were included. Protein-only dipsticks at 1 + threshold had a pooled sensitivity of 0.68 [95%CI: 0.57-0.77] and specificity of 0.85 [95% CI: 0.73-0.93] (n = 3700 urine samples, 18 studies). Higher specificity was found with automatedly (0.93 [95% CI: 0.82-0.98]) compared to visually (0.81 [95% CI: 0.65-0.91]) read dipsticks, whereas sensitivity was similar and costs were higher. The use of albumin-creatinine ratio (ACR) dipsticks was only reported in two studies and did not improve accuracy. Heterogeneity in study design and prevalence of preeclampsia amongst studies complicated interpretation of pooled estimates.

CONCLUSION

Urine dipsticks performed poorly at excluding preeclampsia in hypertensive pregnant women. Further development of accurate and low-cost bedside proteinuria tests is warranted.

Paper-Based Device for Naked Eye Urinary Albumin/Creatinine Ratio Evaluation

This paper introduces the concept of "Drawing-PADs" (Drawing paper-based microfluidic analytical devices) allowing to intuitively evaluate the urinary albumin (Alb) index, a clinically important parameter used for the early detection of renal deficiencies related to diabetes, among others. To enable regular monitoring of the Alb index, a simple examination method suitable for self-diagnosis is highly desirable. The Drawing-PADs rely on the simultaneous naked eye detection of Alb and creatinine (Cre) on a single device according to the distance-based microfluidic PAD (μPAD) approach. The Alb index is visualized by simply drawing a straight line connecting the top of two color-changed assay channel sections (Alb and Cre channels), followed by visually confirming the position of the intercept of the drawn straight line. The semiquantitative Alb index evaluation performed with Drawing-PADs does not require any equipment such as a camera, software, or a color reference chart. The obtained results are independent of the sample volume and are not influenced by changes in the absolute Alb and Cre concentrations caused by urine excretion variations, making spot urine assays possible. Classification of Alb index values according to clinically relevant criteria (normoalbuminuria, microalbuminuria, and macroalbuminuria) is readily achieved within 15 min and has been validated for 15 human urine samples including diabetic patients and healthy volunteers.

Urinary strips for protein assays: easy to do but difficult to interpret!

Urine samples can be readily obtained from patients in everyday clinical practice. Therefore, the availability of urine allows physicians to obtain relevant clinical information in a timely manner. Since the measurement of urinary protein levels is essential in diagnosing and treating a host of diseases, the potential detection of urinary proteins by urinary strips in an easy, quick, and cheap way is very attractive. However, to ensure optimal use of urinary strips, one needs to be aware of their characteristics and their limitations. In this review, we discuss the characteristics of the urinary strips available for testing urinary protein levels and for detecting urinary albumin. We then consider their analytical performances in their most widely used clinical applications (e.g., in pregnancy, chronic kidney disease, diabetes, and screening of the general population).

The efficacy of semi-quantitative urine protein-to-creatinine (P/C) ratio for the detection of significant proteinuria in urine specimens in health screening settings

Background

Urine protein detection could be underestimated using the conventional dipstick method because of variations in urine aliquots. This study aimed to assess the efficacy of the semi-quantitative urine protein-to-creatinine (P/C) ratio compared with other laboratory methods.

Methods

Random urine samples were requested from patients undergoing chronic kidney disease screening. Significant proteinuria was determined by the quantitative P/C ratio of at least 150 mg protein/g creatinine. The semi-quantitative P/C ratio, dipstick protein and quantitative protein concentrations were compared and analyzed.

Results

In the 2932 urine aliquots, 156 (5.3 %) urine samples were considered as diluted and 60 (39.2 %) were found as significant proteinuria. The semi-quantitative P/C ratio testing had the best sensitivity (70.0 %) and specificity (95.9 %) as well as the lowest underestimation rate (0.37 %) when compared to other laboratory methods in the study. In the semi-quantitative P/C ratio test, 19 (12.2 %) had positive, 52 (33.3 %) had diluted, and 85 (54.5 %) had negative results. Of those with positive results, 7 (36.8 %) were positive detected by traditional dipstick urine protein test, and 9 (47.4 %) were positive detected by quantitative urine protein test. Additionally, of those with diluted results, 25 (48.1 %) had significant proteinuria, and all were assigned as no significant proteinuria by both tests.

Conclusions

The semi-quantitative urine P/C ratio is clinically applicable based on its better sensitivity and screening ability for significant proteinuria than other laboratory methods, particularly in diluted urine samples. To establish an effective strategy for CKD prevention, urine protein screening with semi-quantitative P/C ratio could be considered.

Evaluation of the URiSCAN super cassette ACR semiquantitative urine dipstick for microalbuminuria screening

BACKGROUND

Microalbuminuria tests are used as screening tools for diseases, such as diabetic nephropathy, cardiovascular disease, and hypertension. The purpose of this study was to evaluate the utility of a newly introduced semiquantitative urine dipstick, URiSCAN Super cassette ACR (URiSuper-ACR [where ACR is albumin/creatinine ratio]; YD Diagnostics Corp., Korea), as a screening tool for microalbuminuria.

METHODS

Albumin and creatinine levels in randomly selected spot urine samples of 1,040 patients were semiquantitatively measured using URiSuper-ACR. Results using URiSuper-ACR system were compared to measurements obtained by quantitative analyzer. We also calculated diagnostic sensitivity, specificity, precision, linearity, and categorical concordance rates for the diagnosis of microalbumiuria using this system. Furthermore, we performed interference tests using standard controls to evaluate possible influence of various factors.

RESULTS

URiSuper-ACR test showed 88.8% and 86.3% sensitivity and 90.1% and 93.8% specificity for albumin concentration and ACR, respectively. It also showed 91.1% and 92.6% positive predictive values and 87.6% and 88.5% negative predictive values, respectively. The concordance rate between URiSuper-ACR and quantitative method for albumin and creatinine concentration within the same category were 78.4% and 67.1%, respectively, and for the ±1 category were 98.8% and 99.5%, respectively. For ACR, an 80.0% concordance rate was seen within the same category. The within-run coefficients of variation (CVs) were 3.0∼15.4% and 5.2∼23.5% for albumin and creatinine, respectively, showing good linearity. In interference tests, no interference was observed except for cases with high specific gravity.

CONCLUSIONS

URiSuper-ACR showed good diagnostic performance for the detection of microalbuminuria and may be a useful screening test in clinical laboratories.

The relation between estimated glomerular filtration rate and proteinuria in Okayama Prefecture, Japan

OBJECTIVE

We investigated the link between renal function as evaluated by estimated glomerular filtration rate (eGFR) and proteinuria in Okayama Prefecture, Japan.

SUBJECTS AND METHODS

A total of 11030 Japanese subjects, aged between 20 and 79 years, were recruited in a cross-sectional clinical investigation study. eGFR was calculated using serum creatinine, age, and sex. Proteinuria was measured by using urine strip devices.

RESULTS

Age-related variations in eGFR were noted. Two hundred sixteen men (6.2%) and 316 women (4.2%) were diagnosed with trace positive (±) and 140 men (4.0%) and 130 women (1.7%) were diagnosed with positive (+≤) proteinuria. eGFR in subjects with +≤ proteinuria was significantly lower than that in subjects without proteinuria, in both sexes.

CONCLUSION

The present study indicates that proteinuria might be an important marker in the etiology of lower eGFR in Okayama Prefecture, Japan.

Comparison between 24-h proteinuria, urinary protein/creatinine ratio and dipstick test in patients with nephropathy: patterns of proteinuria in dipstick-negative patients

OBJECTIVE

Three main tests are commonly employed for the measurement of proteinuria: the dipstick test, the urinary protein/creatinine ratio (P/C) and the 24-h urine collection. The aim of this study was to evaluate the correlation between these methods, comparing linear regression and ROC curve data.

MATERIAL AND METHODS

A total of 297 consecutive outpatients with different renal diseases were included in the study. Twenty-four-hour proteinuria was considered the reference test.

RESULTS

A high degree of correlation was observed between all the tests (p<0.0001), the highest regression coefficient being between 24-h proteinuria and P/C (R=0.82), and the lowest between P/C and the dipstick test (R=0.72). The dipstick test failed to detect pathological proteinuria in 94 patients (31.6%). Therefore, in these subjects, the patterns of proteinuria were assessed by immunofixation and sodium dodecyl sulphate (SDS) electrophoresis.

CONCLUSIONS

Our data strongly support the use of urinary P/C for the detection of proteinuria, at least in nephrology units, where the prevalence of proteinuria is likely to be high.

Profiling proteinuria in pediatric patients

This study was designed to characterize proteinuria in children with kidney disease. Random urine samples from 250 pediatric patients were examined by quantitative measures of total protein (pr), albumin (Alb), and creatinine (cr). Patient diagnoses were subjectively categorized as "Glomerular" (GD) or "Tubulo-interstitial" disease (TD) in origin. Proteinuria was quantitated by the random urine protein-to-creatinine (Upr/cr) ratio, and glomerular proteinuria was assessed as the albumin-to-creatinine ratio (Ualb/cr) and percentage albuminuria (%Alb=Alb/pr*100). The non-albumin fraction (1-Alb/pr) includes low-molecular-weight proteins and micro- and macroglobulins. Of the 250 patients, 112 (45%) had GD and 138 (55%) had TD. Both proteinuria and albuminuria correlated with a decline in glomerular filtration rate (GFR) (r=-0.4; p<0.0001). Those with GD averaged significantly greater %Alb than those with TD at all levels of proteinuria (p<0.0001). With loss in GFR, %Alb increased significantly in patients with TD (18+/-13 to 47+/-30%; p<0.001) and GD (56+/-26 to 74+/-15%; p<0.01), respectively. The %Alb at all levels of GFR averaged <50% in those with TD and >50% in those with GD. In conclusion, random Ualb/cr, Upr/cr, and %Alb provide a simple and inexpensive assessment of proteinuria and may profile renal disease activity and response to therapy in pediatric patients.

Relationship between metabolic syndrome and proteinuria in the Japanese population

OBJECTIVE

We investigated the link between metabolic syndrome and proteinuria in Japanese.

METHODS

A total of 12,023 Japanese subjects, aged 20-79 years, were recruited in a cross-sectional clinical investigation study. From this group, we used data of 2,121 subjects for further investigation. Proteinuria was measured by using urine strip devices. The diagnosis of metabolic syndrome was based on the new criterion in Japan.

RESULTS

In the first analysis, 224 men (6.0%) and 359 women (4.3%) were diagnosed as trace positive (+/-) and 155 men (4.1%) and 147 women (1.8%) were diagnosed as positive (+< or =) with proteinuria. In the second analysis, 264 men (29.7%) and 45 women (3.7%) were diagnosed as metabolic syndrome. Prevalence of proteinuria in subjects with metabolic syndrome was significantly higher than that in subjects with non metabolic syndrome in both sexes. In addition, the atherogenic index was significantly higher in subjects with metabolic syndrome than in subjects with non-metabolic syndrome.

CONCLUSION

The present study indicated that metabolic syndrome might be an important factor in the etiology of proteinuria in Japanese.

Using protein/creatinine ratios in random urine

We assessed the new test paper Multistix PRO IOLS, in which the +/-region of the conventional test for protein was altered so that creatinine correction became possible. Urinary samples from 235 patients with various renal diseases were obtained from the Juntendo University Hospital. We examined 1) the correlation between qualitatively measured values of urinary protein by the new test paper and the conventional test paper, and 2) the correlation between qualitative and quantitative values of protein (P), creatinine (C), and the P/C ratio measured by the new test paper. There was a good correlation between the P/C ratio observed with the new test paper and that observed by quantitative analysis. There was also a good correlation of the P/C ratio between 24-hr urine and urinary samples obtained at any time of day. Thus, it appears that the results obtained from urinary samples any time of day can predict the amount of protein excreted during the day.

Surface-enhanced laser desorption/ionization-time of flight-mass spectrometry (SELDI-TOF-MS): a new proteomic urinary test for patients with urolithiasis

SELDI-TOF-MS is a highly sensitive protein-analysis tool capable of detecting minute protein profile differences between biological samples. As proteins have been associated with urinary tract calculi, protein-based urinalysis may offer insights into their diagnosis. The purpose of this study was to evaluate SELDI-TOF-MS as a potential method for identifying urinary biomarkers of urolithiasis. Midstream sterile urine samples were obtained from 25 male patients with a confirmed diagnosis of urolithiasis (test group) and 25 male subjects with no known history of the disease (controls). Urinary levels of oxalate, total protein, albumin, and osteopontin were determined. Protein profiles were generated using SELDI-TOF-MS.SELDI-TOF-MS profiling revealed a relationship between protein peak intensities at 67 and 24 kDa that differed between the two groups. The ratio of p67:p24 was found to be less than 1.0 in all of the control samples (mean 0.26), while 18 out of 25 (72%) of the test group samples displayed a ratio greater than 1.0 (total group mean 4.75, P<0.001). Albumin, total protein, and oxalate levels were higher in the test group than the controls. Although SELDI-TOF-MS is not yet in widespread use in hospital and diagnostic laboratories, this system represents a promising new method for rapidly identifying patients with urolithiasis.

Diabetes Mellitus Non-Glucose Monitoring: Point-of-Care Testing

OBJECTIVE:

To review and evaluate reimbursable point-of-care testing devices yielding immediate results, other than glucometers, that are available to evaluate and monitor diabetes and its complications and to describe how pharmacists may use these devices.

DATA SOURCES:

A MEDLINE search (1966-March 2003) was performed using the following search terms: point-of-care systems, clinical diabetes monitoring, decision support systems, glycosylated hemoglobin, and microalbumin. Pertinent company and product Web sites and customer service departments were accessed for information about point-of-care devices and supplies.

STUDY SELECTION AND DATA EXTRACTION:

All descriptive, evaluative, and comparative articles and product information were reviewed, and relevant information was included.

DATA SYNTHESIS:

Diabetes mellitus is a complex, chronic metabolic disease that is a challenging management problem and requires routine monitoring for disease control and screening for complications. Point-of-care tests are available to monitor hemoglobin A1c, glucose, fructosamine, ketones, lipid profiles, urinary microalbumin concentrations, and alanine aminotransferase concentrations. Many of these tests are Clinical Laboratory Improvement Amendments (CLIA)—waived and, therefore, practical for pharmacists to use in a variety of settings. Tests for measuring sensation are also discussed. Pharmacists should consider each of these tests in the establishment of a comprehensive diabetes care service.

CONCLUSIONS:

The availability of many new point-of-care testing methods creates new opportunities for pharmacists to monitor drug therapy and screen for complications in patients with diabetes. Reimbursement is possible since many of these tests are CLIA-waived.

Clinical utility of a rapid test for uristatin

OBJECTIVES

Uristatin is a trypsin inhibitor present in urine that is increased in most patients with bacterial or viral infections and in many with inflammatory disorders. We included the assay of uristatin as part of a screening program carried out by pediatricians on 4207 Japanese schoolchildren to judge the ability of uristatin to identify those with an infection and (or) inflammation of any cause. We used urine dipsticks for the assay of uristatin, creatinine, albumin, blood, leukocyte esterase, and protein. We also performed quantitative assays for uristatin and creatinine. Another aim was to estimate the reference range for uristatin in schoolchildren, ages 5 to 14 yr.

METHODS

We prepared dipstick pads that were impregnated with a chromogenic substrate for trypsin and measured the uristatin-caused inhibition of trypsin in urine. We measured creatinine so that the ratio of uristatin to creatinine could be calculated to correct for urine concentration.

RESULTS

We obtained quantitative uristatin and creatinine results for 4207 children. Of these, 177 had an abnormal urine dipstick for albumin or blood or protein or leukocyte esterase or a combination of these. We used data from 3622 children to establish the reference range for the uristatin dipsticks. The 3622 were diagnosed by their pediatricians as free from an infection or inflammation of any cause and with normal urine dipstick tests. We recommend an upper reference limit for uristatin by dipstick of < or = 7.5 mg uristatin/g creatinine. The leftover 408 children ( [4207-3622-177] = 408) fell into two groups: 205 with diagnoses of no infection, possible infection, or possible inflammatory disorders. The remaining 203 children were renal disease follow-up cases. The diagnoses were based on a physical examination, microscopic urinalysis plus urine dipstick tests for albumin, blood, creatinine, protein, leukocyte esterase and a complete blood count. In the 205 children, 46 had an abnormal uristatin dipstick test, 39 had an abnormal uristatin by immunoassay, 41 had an abnormal erythrocyte sedimentation rate (ESR), 27 had an abnormal serum C-reactive protein (CRP), and one had an abnormal urine microscopic exam. For the first 938 children in the study, the agreement was 93% of negative dipstick uristatin results and immunoassays. The agreement of positive uristatin dipsticks with immunoassays was 85%. We assumed that the immunoassay results were correct. In the evaluation of 189 children with fever, 62 also had an abnormal uristatin by dipstick.

DISCUSSION

A rapid dipstick test for uristatin read on a reflectance photometer gave values that compared well with a quantitative immunoassay method. The uristatin test is sensitive but not specific for any cause of infection or inflammation. Uristatin is easy to determine and appears to be a better indicator than fever, ESR, or CRP for the diagnosis of an infection or inflammation.