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LETTER TO EDITOR
Year : 2018  |  Volume : 7  |  Issue : 5  |  Page : 1148-1149  

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


1 Department of Public Health, School of Health, Semnan University of Medical Sciences, Semnan; Department of Clinical Epidemiology, School of Public Health, Shahid Beheshti University of Medical Sciences, Tehran, Iran
2 Department of Community Medicine, School of Medicine; Social Determinants of Health Research Center, Ardabil University of Medical Sciences, Ardabil, Iran
3 Department of Clinical Epidemiology, School of Public Health; Safety Promotion and Injury Prevention Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran

Date of Web Publication20-Nov-2018

Correspondence Address:
Dr. Siamak Sabour
Department of Clinical Epidemiology, Safety Promotion and Injury Prevention Research Center, School of Health, Shahid Beheshti University of Medical Sciences, Tehran
Iran
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jfmpc.jfmpc_224_18

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How to cite this article:
Pordanjani SR, Iranpour S, Sabour S. The reliability and validity of using the urine dipstick test by patient self-assessment for urinary tract infection screening in spinal cord injury patients: Methodological and statistical issues on reliability and validity. J Family Med Prim Care 2018;7:1148-9

How to cite this URL:
Pordanjani SR, Iranpour S, Sabour S. The reliability and validity of using the urine dipstick test by patient self-assessment for urinary tract infection screening in spinal cord injury patients: Methodological and statistical issues on reliability and validity. J Family Med Prim Care [serial online] 2018 [cited 2019 Sep 20];7:1148-9. Available from: http://www.jfmpc.com/text.asp?2018/7/5/1148/245757



Dear Editor,

We were interested to read the recent paper by Krit Duanngai and colleagues published in September 2017 issue of the J Family Med Prim Care.[1]

The authors aimed 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. The inter-rater reliability was measured in the sense of Kappa and validity of urine dipstick test was reported in terms of sensitivity, specificity, positive and negative likelihood ratio (+LR, −LR), positive predictive value (PPV), and negative predictive value (NPV). 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 combined leukocyte esterase and nitrite urine dipstick test gave the highest specificity (87%), PPV (60%), and NPV (93%). According to the validity of urine dipstick test +LR for leukocyte esterase was 1.33 with 95% confidence interval (CI) (0.40–4.42) and −LR was 0.94 with 95% CI (0.74–1.21).

However, these results are not the most appropriate estimates to evaluate validity and reliability. Kappa has two crucial disadvantages; first, it depends on the prevalence in each category and the second weaknesses of the Kappa value is the fact that it depends on the number of categories.[2],[3],[4] To assess reliability (agreement), appropriate methods are the intraclass correlation coefficient (ICCC) or Bland–Altman plot for quantitative variables and weighted Kappa for the qualitative variable with more than two categories.[2],[3],[4]

Moreover, we surprised when we looked at the range of LR+ and LR−. To the best of our knowledge, LR+ can be changed from 1 to ∞ (the higher the LR+, the more accurate the test) and LR− can be changed from 0 to 1 (the closer the LR− to 0, the more accurate the test). Theoretically, when the value of LR+ is <1 and LR− is >1, the diagnostic accuracy of the test is worse than flipping a coin![4],[5] We are facing such a situation in this study when looking at the 95% CI of the LR+. It means the accuracy of the mentioned tests is not acceptable and should not be suggested for clinical purposes.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Duanngai K, Sirasaporn P, Ngaosinchai SS. The reliability and validity of using the urine dipstick test by patient self-assessment for urinary tract infection screening in spinal cord injury patients. J Family Med Prim Care 2017;6:578-82.  Back to cited text no. 1
[PUBMED]  [Full text]  
2.
Szklo M, Nieto FJ. Epidemiology beyond the Basics. 3rd ed. Burlington, MA: Jones and Bartlett; 2014.  Back to cited text no. 2
    
3.
Sabour S. Reliability of automatic vibratory equipment for ultrasonic strain measurement of the median nerve: Common mistake. Ultrasound Med Biol 2015;41:1119-20.  Back to cited text no. 3
    
4.
Sabour S. Adherence to guidelines strongly improves reproducibility of brachial artery flow-mediated dilation. Common mistakes and methodological issue. Atherosclerosis 2016;251:490-1.  Back to cited text no. 4
    
5.
Robert M. Centor. Estimating confidence intervals of likelihood ratios. Med Decis Making 1992;12:229-33.  Back to cited text no. 5
    




 

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