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CC BY-NC-ND 4.0 · J Lab Physicians 2022; 14(01): 043-046
DOI: 10.1055/s-0041-1739537
Original Article

Evaluation of Tear Film Urea Level as a Diagnostic Marker of Dry Eye Disease: A Pilot Study

Gurunadh Satyanarayana Velamakanni 
1   Department of Ophthalmology, GSL Medical College, Rajahmundry, Andhra Pradesh, India
,
Anil Sharma
2   Department of Ophthalmology, Military Hospital, Jhansi, Uttar Pradesh, India
,
Hitender S. Batra
3   Department of Biochemistry, Military Hospital, Kirkee, Pune, Maharashtra, India
,
Subrahmanya Murti Velamakanni 
4   Department of Cardiology, Smt NHL Municipal Medical College, Ahmedabad, Gujarat, India
,
Mansur Khan
5   Department of Ophthalmology, Command Hospital Air Force, Bengaluru, Karnataka, India
,
Sandeep Gupta
6   Department of Ophthalmology, Command Hospital, Chandigarh, India
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Abstract

Introduction Urea secreted in the sweat is important for skin moisture. Similarly, ocular surface moisture is maintained by the conjunctiva. Based on this, the level of urea in tear film can be used as a potential diagnostic test for dry eye disease (DED). One of the standard tests for DED is Schirmer's test (ST). The aim of this study was to compare tear film urea to values of ST.

Methods Fifty patients symptomatic for DED having ST ≤ 10 mm/5 min were enrolled in the study. Fifty age- and sex-matched asymptomatic subjects with ST > 10 mm/5 min were taken as controls. All patients were subjected to an estimation of tear film urea, collected using micropipettes, and analyzed by an Erba Chem 5 semi-autoanalyzer. Based on the ST reading as per the Dry Eye Workshop 2007 (DEWS) classification, dry eye was classified as dry eye (≤ 10 mm/5 min), severe dry eye (≤ 5 mm/5 min), and very severe dry eye (≤ 2 mm/5 min). Tear film urea values were compared with ST values that were considered standard. Statistical analysis was done using Medcalc version 19.7. A p-value ≤ 0.05 was considered significant.

Results The mean tear film urea levels in cases were (26.78 ± 5.70 mg/dL) significantly lower compared with controls (41.72 ± 6.86 mg/dL). The area under the receiver characteristic operator curve (AUC) for tear film urea in diagnosing DED was 0.936 (p < 0.0001) with a cutoff of ≤ 37.2 mg/dL, yielding a sensitivity of 96% and a specificity of 76%. For diagnosing severe DED, the AUC for tear film urea was 0.824 (p < 0.0001) with a cutoff value of ≤ 23.4 mg/dL, yielding a sensitivity of 60.8% and a specificity of 92.59%. For diagnosis of very severe DED, the AUC for tear film urea was 0.972 (p < 0.0001) with a cutoff value of ≤ 19.8 mg/dL, yielding a sensitivity of 100% and a specificity of 93.62%. On comparing ST values to tear film urea, the regression coefficient was 0.85 (p < 0.0001), suggesting a linear relationship between ST and tear film urea.

Conclusion The study demonstrates that tear film urea can be a potential diagnostic marker for DED. The study also indicates that tear film urea level is linearly related to Schirmer's test values and provides an approximate diagnostic cutoff level for the design of future large-scale studies.

Keywords

dry eye disease - Schirmer's test - tear film urea

Institutional Approval

This work received an institutional review and ethical approval from the ethics committee of the Armed Forces Medical College, Pune.




Publikationsverlauf

Artikel online veröffentlicht:
23. November 2021

© 2021. The Indian Association of Laboratory Physicians. This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/)

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