|Year : 2016 | Volume
| Issue : 2 | Page : 62-66
Diagnostic performance of urine dipstick test for urinary tract infection screening in individuals with spinal cord injury
Department of Rehabilitation, Srinagarind Hospital, Khon Kaen University, Khon Kaen, Thailand
|Date of Web Publication||18-May-2016|
Department of Rehabilitation, Faculty of Medicine, Srinagarind Hospital, Khon Kaen University, Khon Kaen
Source of Support: None, Conflict of Interest: None
Objectives: To determine the diagnostic performance of urine dipstick test for urinary tract infection (UTI) screening in spinal cord injury (SCI) patients. Study Design: A cross-sectional diagnostic study. Setting: Srinagarind Hospital, Khon Kaen, Thailand. Participants: SCI patients with neurogenic bladder. Materials and Methods: This study was a cross-sectional diagnostic study that compared the urine dipstick test (index test) with the National Institute on Disability and Rehabilitation Research (NIDRR) criteria (gold standard test) in SCI patients. The urine dipstick test reported positive and negative results. Moreover, the NIDRR criteria classified participants as patients with UTI and patients with no UTI. The diagnostic performance of urine dipstick test for UTI screening was measured in terms of sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (+LR), and negative likelihood ratio (-LR) and was summarized in percentage with 95% confidence interval (CI). Results: Out of the 77 participants, most of participants were paraplegia (74%). The combined nitrite and leukocyte esterase urine dipstick test showed the highest sensitivity (93%), PPV (79%), NPV (85%), and +LR (2.39), respectively. The urine dipstick test of nitrite gave the highest specificity (69%). The most common uropathogen was Escherichia coli (33%). Conclusion: In SCI patients, the combined positive nitrite and leukocyte esterase urine dipstick test showed the highest sensitivity. The combined nitrite and leukocyte esterase urine dipstick test should be promoted as a screening test for UTI in SCI patients.
Keywords: Neurogenic bladder, urinary tract infection (UTI), urine dipstick test
|How to cite this article:|
Sirasaporn P. Diagnostic performance of urine dipstick test for urinary tract infection screening in individuals with spinal cord injury. J Sci Soc 2016;43:62-6
|How to cite this URL:|
Sirasaporn P. Diagnostic performance of urine dipstick test for urinary tract infection screening in individuals with spinal cord injury. J Sci Soc [serial online] 2016 [cited 2020 Aug 13];43:62-6. Available from: http://www.jscisociety.com/text.asp?2016/43/2/62/182595
| Introduction|| |
Spinal cord injury (SCI) produces alteration in urological function and often requires the use of bladder management for urine drainage, using indwelling urethral, clean intermittent catheterization, and urinary condom catheters. Moreover, their urological problems relate to many complications such as vesicoureteral reflux, hydronephrosis, and urinary tract infection (UTI). 
UTI is the most common complication in SCI patients.  They frequently undergo antibiotic treatment. Despite advances in antibiotic treatment and early interventions, SCI patients continue to have UTI problems.  Risk factors for UTI in SCI patients are overdistension of bladder, vesicoureteric reflux, high pressure voiding, presence of stone in the urinary tract, detrusor sphincter dyssynergia, inadequate fluid intake, level of disability, and method of bladder management. 
The clinical diagnosis of UTI in the general population is typically established by assessing for key symptoms such as dysuria, flank pain, and increased urinary frequency together with finding evidence of the presence of bacteria or inflammation in the urinary tract by using urine analysis and urine culture. Although this approach is useful for the general population, it is not applicable to individuals with SCI because of their neurological abnormalities and common abnormal voiding patterns.  Besides, some SCI patients have urological anatomy and physiology abnormalities. These patients do not complain of dysuria or flank pain or increased urinary frequency.  Nevertheless, a standard test for UTI diagnosis in SCI patients is quoted from the National Institute on Disability and Rehabilitation Research (NIDRR). The NIDRR  consensus statement sets the criteria for the diagnosis of UTI in person with SCI by using significant bacteriuria (intermittent catheterization: U/C > 10 2 CFU/mL; urinary condom: U/C > 10 4 CFU/mL; indwelling catheterization: U/C = any detectable concentration) and the presence of at least one sign or symptom of UTI (leukocytes in the urine, cloudy urine with increased odor, increased spasticity, lethargy, fever, urinary incontinence, autonomic dysreflexia, malaise, sense of unease, and discomfort or pain during urination).
In addition, the criteria of NIDRR is required the urine culture result that needs an incubation period of 24 h or more. It causes delay in treatment of SCI patients. Some physicians starts the antibiotic treatment depending on the urine culture result. This condition may lead to antibiotic overtreatment and further contribute to antibiotic resistance rates. Not only incubation period of urine culture but also lack of urine culture serving in some medical facilities is mentioned. Therefore, urine culture is not available in those places.
Urine dipstick test that includes leukocyte esterase and nitrite is the only option for UTI screening.  When the reagent on the dipstick detects nitrite in urine, it means there might be some bacteria that reduces nitrates to nitrites, and it indicates bacteriuria. Besides, reagent detection of leukocytes esterase during urine analysis can be related to pyuria. The urine dipstick test can be used for the screening of UTI and it reduces the number of negative urine sample sent for urine culture. Moreover, the urine dipstick test is less time-consuming, less expensive, and easy to apply by the community-based nursing staff, the patients, or their caregivers.
In recent times, there has been an increased understanding of how to evaluate the usefulness of urine dipstick that is frequently used in different population such as children, pregnant women, and the elderly. ,,,,,, The urine dipstick test seems to be useful in detecting the presence of UTI.  However, the studies of urine dipstick in SCI patients were not well-known. The sensitivity and specificity of urine dipstick test were about 23-100% and 52-99%, respectively. ,,,,, The PPV and NPV were about 33-96% and 88-100%, ,,,,, respectively. All of studies compared the urine dipstick with only urine culture and urine analysis that were not the standard criteria for UTI diagnosis in SCI patients. So, no previous studies compared the urine dipstick test with the NIDRR criteria.
This study aimed to determine the diagnostic performance of leukocyte esterase and nitrite urine dipstick test for UTI screening in SCI patients and keeping NIDRR as the gold standard for the diagnosis of UTI.
| Materials and methods|| |
SCI patients with neurogenic bladder attended the Department of Rehabilitation, Srinagarind Hospital, during March 2014 to December 2014. Inclusion criteria were age more than 18 years and history of neurogenic bladder of more than 6 months. Exclusion criteria were pregnancy, diabetes mellitus, stones or tumor in urinary tract, and taken ascorbic acid more than 500 mg/day within 1 week prior to study. This study was approved by the Khon Kaen University Ethics Committee for Human Research (HE561492) and was supported by the Faculty of Medicine Research Fund, Khon Kaen University (I57226).
The Participants were assessed by questionnaire, NIDRR criteria, and urine dipstick test. The method was shown as STARD flow diagram [Figure 1]. The questionnaire included questions regarding age, sex, neurological level, American Spinal Injury Association (ASIA) classification, duration of injury, type of bladder management, and presence of vesicoureteric reflux, and hydronephrosis. NIDRR criteria, which was a gold standard test was evaluated by taking urine culture and checking the presence of sign or symptom of UTI. The urine dipstick test was done using AUTION sticks 10 EA (Axon Lab AG, Germany). The urine reagent pad was dipped into urine for 2 s and colorations were interpreted after dipping it for 2 min. To decrease the inter-rater variation in manual reading of the urine dipstick result, the interpretation was done by using an ARKRAY urine analyzer. Urine dipstick test that was an index test reported leukocyte and nitrite levels as positive and negative. Moreover, the NIDRR criteria and urine dipstick test were conducted independently and blinded to the results of the other.
Data from all participants will be analyzed according to data being available. No imputation will be implemented to missing data. All statistical tests will be two-sided with a significant level of 0.05. All statistical analysis will be implemented by using Stata 12 (StataCorp, College Station, TX). All baseline characteristics were summarized in number percentage unless specified of age and duration of injury in mean and standard deviation. The diagnostic performance were calculated in term of sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (+LR), and negative likelihood ratio (-LR). All of diagnostic performance value and its 95% confidence interval (CI) were demonstrated.
| Result|| |
The number of participants was 77 out of whom 51 (66.2%) were males. The average age was 46.7 + 16.9 years old. Duration of SCI was 6.8 + 9.8 years. Most of neurological level was paraplegia (74%). Most of participants were classified in ASIA C classification (27.3%). Indwelling catheterization was the most type of bladder management (50.6%). Nineteen participants had history of vesicoureteric reflux, whereas eight participants had history of hydronephrosis [Table 1]. Moreover, the most common pathogen microorganism was Escherichia More Details coli (75%) [Table 2].
According to diagnostic performance of urine dipstick test, the urine dipstick test of combined leukocyte esterase and nitrite showed the highest sensitivity (93%), PPV (79%), and NPV (85%), respectively. The highest specificity was the urine dipstick test of nitrite (69%). The highest +LR (2.39) and the lowest -LR (0.11) was the urine dipstick test of both leukocyte esterase and nitrite [Table 3].
| Discussion|| |
The diagnostic performance of the urine dipstick test for UTI was compared with gold standard test (NIDRR). In this study, the urine dipstick test of combined leukocyte esterase and nitrite was more sensitive than the urine dipstick test of either leukocyte esterase or nitrite that was accorded with the previous studies. ,, The sensitivity of nitrite test when used individually is not reliable to rule out UTI in most patients unlike the findings of the previous studies. , Regarding to PPV, probability that the UTI was present when the urine dipstick test of combined positive leukocyte esterase and nitrite was good as the former study.  Concerning NPV, chance to predict no UTI, when the urine dipstick test of negative combined leukocyte esterase and nitrite was high that was accorded with some prior studies. , Moreover, +LR of the combined leukocyte esterase and nitrite urine dipstick test was greater than one that reflected increasing the probability that UTI was present. Therefore, combined positive leukocyte esterase and nitrite is a better way for screening UTI in SCI patients. In contrast, the urine dipstick test of nitrite was the most specific but the least sensitivity as the previous study. 
The diagnostic performance of urine dipstick for screening UTI has been studied widely, but results of these researches are varied depending on patient population, laboratory techniques, and gold standard test. This study was performed with specific populations - SCI patients who usually had different neurological function compared to general population. Besides, the gold standard test in this study was NIDRR that was specific to UTI diagnosis in SCI patients. This is the first study that compares the urine dipstick test with the NIDRR criteria. Thereby, this study suggests that the combined leukocyte esterase and nitrite urine dipstick test may help the primary health-care physicians to make decisions before UTI is confirmed by the urine culture. In addition, the urine dipstick test is easy to perform and can be provided by medical personnels without specific laboratory technique training. This test can also be done by individuals with SCI who are able to perform hand motor function and physical performance.
| Conclusion|| |
Although NIDRR is the gold standard test for the diagnosis of UTI in SCI patients, urine dipstick test of combined leukocyte esterase and nitrite is very useful for urinary infection screening that reflects relatively accurate results. Moreover, it is inexpensive widely used, and can be done in medical facilities where the urine culture is not available. Therefore, the urine dipstick test of combined leukocyte esterase and nitrite should be promoted as a screening test for UTI in SCI patients. In addition, Escherichia coli is the commonest uropathogen in SCI patients with UTI.
Financial support and sponsorship
Supported by Faculty of Medicine Research Fund, Khon Kaen University (I56334).
Conflicts of interest
No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit on the authors or on any organization with which the authors is associated.
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[Table 1], [Table 2], [Table 3]