Journal of Cytology
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Year : 2019  |  Volume : 36  |  Issue : 3  |  Page : 185-186
Reproducibility of the Bethesda system for reporting thyroid cytopathology: A methodological issue

1 Department of Operating Room, School of Paramedical, Kermanshah University of Medical Sciences, Kermanshah, Iran
2 Department of Clinical Epidemiology, School of Public Health; Safety Promotions and Injury Prevention Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran

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Date of Web Publication18-Jun-2019

How to cite this article:
Naderi M, Sabour S. Reproducibility of the Bethesda system for reporting thyroid cytopathology: A methodological issue. J Cytol 2019;36:185-6

How to cite this URL:
Naderi M, Sabour S. Reproducibility of the Bethesda system for reporting thyroid cytopathology: A methodological issue. J Cytol [serial online] 2019 [cited 2020 Jan 21];36:185-6. Available from:

Dear Editor,

We were interested to read the article by Awasthi et al. published in the March 2018 issue of J Cytol.[1] They aimed to assess the reproducibility of “The Bethesda System for Reporting Thyroid Cytopathology” (TBSRTC) for diagnosing thyroid lesions. Wright Giemsa and Papanicolaou-stained fine-needle aspiration cytology smears along with relevant clinical and radiological details of 107 patients having a non-TBSRTC diagnosis were analyzed by two trained cytopathologists.[1] The interobserver variation and reproducibility of the reporting system was assessed by Cohen's kappa coefficient.[1]

First of all, it is very important to know that there is no value of kappa that can be regarded universally as an indication of good agreement. Two important weaknesses of kappa to assess agreement of a qualitative variable are as follows. First, it depends on the prevalence in each category, which means it can be possible to have different k values having the same percentage for both concordant and discordant cells. [Table 1] shows that in both (a) and (b) situations, the prevalence of concordant cells is 90% and of discordant cells is 10%; however, we get different kappa values (0.44 as moderate and 0.80 as very good, respectively). Kappa value also depends on the number of categories.[2],[3],[4],[5],[6] In this study, since we face a five-state variable, it is better to apply weighted kappa to avoid misinterpretation.
Table 1: Comparison of two cytopathologists' diagnoses with different prevalence in the two categoriesa

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They concluded that TBSRTC is a distinctive, universal, and homogeneous terminology for reporting thyroid cytology, and its execution should be promoted because of its virtual ease of reproducibility. Due to the above-mentioned limitations of kappa value to assess reproducibility, such a conclusion may be a misleading message.[2],[3],[4],[5],[6]

In this letter, we discussed limitations of kappa value to assess reproducibility. Therefore, any conclusion especially in clinical practice should be supported by the above-mentioned statistical and methodological issues. Otherwise, mismanagement of the patients cannot be avoided.

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Conflicts of interest

There are no conflicts of interest.

   References Top

Awasthi P, Goel G, Khurana U, Joshi D, Majumdar K, Kapoor N. Reproducibility of “The Bethesda System for Reporting Thyroid Cytopathology”: A retrospective analysis of 107 patients. J Cytol 2018;35:33-6.  Back to cited text no. 1
[PUBMED]  [Full text]  
Szklo M, Nieto FJ. Epidemiology beyond the Basics. 2nd ed. Manhattan: Jones and Bartlett Publisher; 2007.  Back to cited text no. 2
Sabour S. Reproducibility of endometrial cytology by the Osaki Study Group Method: Methodological issues. Cytopathology 2017;28:441-2.  Back to cited text no. 3
Sabour S. Reliability of immunocytochemistry and fluorescence in situ hybridization on fine-needle aspiration cytology samples of breast cancers: Methodological issues. Diagn Cytopathol 2016;44:1128-9.  Back to cited text no. 4
Sabour S. Spinal instability neoplastic scale: Methodologic issues to avoid misinterpretation. AJR Am J Roentgenol 2015;204:W493.  Back to cited text no. 5
Sabour S, Dastjerdi EV. Reliability of four different computerized cephalometric analysis programs: A methodological error. Eur J Orthod 2013;35:848.  Back to cited text no. 6

Correspondence Address:
Dr. Siamak Sabour
Department of Clinical Epidemiology, School of Health, Safety Promotion and Injury Prevention Research Centre, Shahid Beheshti University of Medical Sciences, Chamran Highway, Velenjak, Daneshjoo Blvd, Tehran 198353-5511
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/JOC.JOC_44_18

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