Sex differences in the evaluation of proteinuria using the urine dipstick test

Background

The urine protein dipstick test is widely used, but false-positive and false-negative results may occur. This study aimed to compare the urine protein dipstick test with a urine protein quantification method.

Methods

The data were extracted using the Abbott Diagnostic Support System, which analyzes the inspection results using multiple parameters. This study included 41,058 specimens tested using the urine dipstick test and protein creatinine ratio from patients aged ≥18 years. The proteinuria creatinine ratio was classified according to the Kidney Disease Outcomes Quality Initiative guidelines.

Results

Urine protein on the dipstick test was negative in 15,548 samples (37.9%), trace in 6,422 samples (15.6%), and ≥1+ in 19,088 samples (46.5%). Among the trace proteinuria samples, A1 (<0.15 g/gCr), A2 (0.15-0.49 g/gCr), and A3 (≥0.5 g/gCr) category proteinuria accounted for 31.2, 44.8, and 24.0% of samples, respectively. All trace proteinuria specimens with a specific gravity of <1.010 were classified as A2 and A3 category proteinuria. In the trace proteinuria cases, women had a lower specific gravity and a higher percentage of A2 or A3 category proteinuria than men. The sensitivity in the "dipstick proteinuria" ≥ trace" group was higher than that in the "dipstick proteinuria ≥ 1+" group within the lower specific gravity group. The sensitivity in the "dipstick proteinuria ≥ 1+" group was higher for men than for women, and the sensitivity in the "dipstick proteinuria ≥ trace" group was higher than that in the "dipstick proteinuria ≥ 1+" group for women.

Conclusion

Pathological proteinuria assessment requires caution; this study suggests that evaluating the specific gravity of urine specimens with trace proteinuria is essential. Particularly for women, the sensitivity of the urine dipstick test is low, and caution is needed even with trace specimens.

Nitrite-negative results in urinary tract infection by Enterobacterales: does the nitrite dipstick test have low sensitivity?

Urinary tract infection (UTI) is one of the most common bacterial infections among humans. Urine culture is the gold standard diagnostic method for UTI; however, the dipstick test for nitrite is a widely used method signalling the presence of urinary nitrate-reducing bacteria. Unlike the gold standard, the dipstick test is easy to perform, while it is also less time-consuming and less expensive, and produces a result in a few minutes. This study investigates the sensitivity of the dipstick test for nitrite compared with the Griess test in urine samples from UTI caused by Enterobacterales species. We used the Griess test, which is the gold standard in nitrite measurement, to determine the sensitivity of the nitrite dipstick test. Semiquantitative urine culture was performed using standard procedures, and Enterobacterales identification was performed by manual conventional biochemical tests. In the first sample selection, 3 % (8/267) of urine samples suspected of UTI, analysed from March to April 2016, were nitrite-negative by dipstick test but positive for Enterobacterales in the urine culture. In the second sample selection, 5 % (2/44) of urine samples from October to December 2022 were also nitrite-negative but showed urine Enterobacterales isolation. All nitrite-negative dipstick results were consistent with the Griess test. Escherichia coli was the most prevalent bacterium, followed by Klebsiella pneumoniae, independent of sample selection. The dipstick test is a safe alternative for investigating nitrite in urine samples. We believe that the cause of nitrite-negative results is a lack of dietary nitrate, dilution of urine and exogenous interference (e.g. ascorbic acid). These findings support the idea that standard urine culture is necessary to rule out UTI.

Low urine pH associated with sarcopenia in the elderly: A multi-center observational study

The pathophysiology of sarcopenia is complex and must be further explored. While metabolic acidosis may be a risk factor for sarcopenia, it remains unclear whether acidic urine is related to sarcopenia. The purpose of the present study was to investigate the association between sarcopenia and urine pH in the elderly.An elderly population (n = 123 [male = 46]; mean age = 81.7 years) was classified into 2 groups based on the sarcopenia status according to their strength, requirement of assistance in walking, their ability to rise from a chair their ability to climb stairs, and their history of falls. Urinalysis was measured using dipstick tests.The sarcopenia group (n = 32) was significantly older, had less exercise habit and showed a lower urine pH (mean pH = 5.5) in comparison to the nonsarcopenia group (mean pH = 6.2, P < .01). A multivariate analysis that was adjusted for age, male sex, body mass index, uro-renal variables and exercise habit revealed that urine pH (odds ratio, 0.43; 95% confidence interval, 0.22-0.85, P = .02), age and less exercise habit were independently and significantly associated with sarcopenia.The findings of the present study suggest a potential association between metabolic acidosis and the pathophysiology of sarcopenia in the elderly. As urine pH is a simple biomarker that can be obtained using dipstick tests, it is therefore expected to be helpful for detecting sarcopenia in the clinical setting.

The Level of Urine Dipstick Proteinuria and Its Relation to the Risk of Incident Cholelithiasis

Background

Previous studies have suggested the potential association between renal diseases and gallstone. The extent of proteinuria is recognized as a marker for the severity of chronic kidney disease. However, little data is available to identify the risk of incident gallstone according to the level of proteinuria.

Methods

Using a data of 207,356 Koreans registered in National Health Insurance Database, we evaluated the risk of gallstone according to the levels of urine dipstick proteinuria through an average follow-up of 4.36 years. Study subjects were divided into 3 groups by urine dipstick proteinuria (negative: 0, mild: 1+ and heavy: 2+ or greater). Multivariate Cox-proportional hazard model was used to assess the adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for incident cholelithiasis according to urine dipstick proteinuria.

Results

The group with higher urine dipstick proteinuria had worse metabolic, renal, and hepatic profiles than those without proteinuria, which were similarly observed in the group with incident cholelithiasis. The heavy proteinuria group had the greatest incidence of cholelithiasis (2.39%), followed by mild (1.54%) and negative proteinuria groups (1.39%). Analysis for multivariate Cox-proportional hazard model indicated that the heavy proteinuria group had higher risk of cholelithiasis than other groups (negative: reference, mild proteinuria: HR 0.97 [95% CI, 0.74–1.26], and heavy proteinuria: HR 1.46 [95% CI, 1.09–1.96]).

Conclusion

Urine dipstick proteinuria of 2+ or greater was significantly associated with increased risk for incident gallstone.

Chronic renal dysfunction, proteinuria, and risk of Parkinson's disease in the elderly

BACKGROUND

The roles of chronic kidney disease and proteinuria in the development of Parkinson's disease have not been widely studied. The objective of this study was to examine the associations of chronic renal dysfunction and proteinuria with the risk of PD in older adults using cohort data of the whole South Korean population.

METHODS

We included 3,580,435 individuals aged ≥65 years who had undergone health checkups provided by the National Health Insurance Service of South Korea between 2009 and 2012 and were followed until 2015. Multivariable Cox proportional hazards regression models were performed.

RESULTS

During a mean follow-up of 5.2 ± 1.3 years, 30,813 individuals (0.86% of the total population) developed PD. Lower estimated glomerular filtration rate and a higher degree of proteinuria on a dipstick test were associated with higher incidence probability of PD (log-rank P < 0.001). In Cox regression models, chronic renal dysfunction graded by estimated glomerular filtration rate (mL/min/1.73 m² ) was associated with increased risk of PD after adjusting for potential confounding variables; hazard ratio (95% confidence interval) was 1.13 (1.10-1.17) for estimated glomerular filtration rate 60-90, 1.36 (1.31-1.42) for estimated glomerular filtration rate 30-60, and 1.47 (1.32-1.63) for estimated glomerular filtration rate <30 (P for trend <0.001). Proteinuria ≥1+ was also associated with increased risk of PD development (hazard ratio, 1.12; 95% confidence interval, 1.06-1.18). Coexistence of chronic kidney disease and proteinuria showed an increased hazard ratio of 1.33 (95% confidence interval, 1.23-1.45) for PD occurrence.

CONCLUSIONS

Our findings suggest that chronic renal dysfunction and dipstick-positive proteinuria may be independent risk factors for the development of PD in older adults. © 2019 International Parkinson and Movement Disorder Society.

The reliability and validity of using the urine dipstick test by patient self-assessment for urinary tract infection screening in spinal cord injury patients

Aims:

The aim of this is to evaluate the reliability of the urine dipstick test by patients’ self-assessment for urinary tract infection (UTI) screening and to determine the validity of urine dipstick test.

Settings:

Rehabilitation Department, Srinagarind Hospital, Thailand.

Study Design:

A diagnostic study.

Subjects and Methods:

This study compared the urine dipstick test (index test) with the National Institute on Disability and Rehabilitation Research (NIDRR) criteria (gold standard test) in spinal cord injury (SCI) patients. The urine dipstick test informed positive and negative results. Besides the NIDRR criteria classified as UTI and no UTI. The interrater reliability was measured in the sense of Kappa whereas the validity of urine dipstick test was reported in terms of sensitivity, specificity, positive likelihood ratio (LR) (+LR), negative LR (−LR), positive predictive value (PPV), and negative predictive value (NPV).

Results:

Out of the 56 participants, the kappa of urine dipstick test for leukocyte esterase, nitrite, and combined leukocyte esterase and nitrite were 0.09, 0.21, and 0.52, respectively. The nitrite urine dipstick test showed the highest sensitivity (90%). The combined leukocyte esterase and nitrite urine dipstick test gave the highest specificity (87%), PPV (60%), NPV (93%), and +LR (5.63).

Conclusions:

The interrater reliability of combined leukocyte esterase and nitrite urine dipstick test was moderate agreement. The combined leukocyte esterase and nitrite urine dipstick test showed high level of both sensitivity and specificity. The combined leukocyte esterase and nitrite urine dipstick test should be promoted for patients’ self-assessment for UTI screening in SCI patients.

The influence of vitamin C on the urine dipstick tests in the clinical specimens: a multicenter study

BACKGROUND

Vitamin C may interfere with the results of urine dipstick tests. We investigated the incidence of urinary vitamin C and its interference with urine dipstick reagents using a vitamin C dipstick.

METHODS

The incidence of urinary vitamin C was determined in patients and healthy individuals undergoing routine medical check-ups. Interference tests were performed using samples with various amounts of added vitamin C. For clinical samples, we identified false-negative dipstick glucose, hemoglobin, and leukocyte esterase results based on the urine sediment and serum glucose results.

RESULTS

Vitamin C was found in the urine of 18.1% of the subjects overall, and 23.1% of those undergoing medical check-ups. Dipstick results for glucose, leukocyte esterase, and hemoglobin differed between samples without vitamin C and with added vitamin C. When vitamin C was detected in clinical urine samples, 42.3%, 10.6%, and 8.2% of the glucose, hemoglobin, and leukocyte esterase dipstick tests were rated as false negative, respectively.

CONCLUSIONS

Vitamin C was frequently found in clinical urine samples, and its concentration was higher in individuals undergoing medical check-ups. Urinary vitamin C can interfere with the urine dipstick results. This study gives useful information for predicting false-negative rates of urine dipstick tests caused by vitamin C.