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Assessments of the size of tympanic membrane perforations: a comparison of clinical estimations with video-otoscopic calculations.

Abstract

We conducted a study to determine how accurate various ENT specialists were in estimating the size of 100 tympanic membrane (TM) perforations with standard otoscopy. The specialists included, in descending order of rank, 2 Consultant Surgeons, 2 Senior Registrars, and 2 Registrars, all of whom had confirmed good vision. We compared their estimates, which were made independently and expressed as a percentage of the total area of the TM, with exact measurements calculated with computer-based video-otoscopy. We found that the video-otoscopic calculations were far superior to the estimates of the specialists, even the most experienced Consultants (p < 0.01). We recommend that video-otoscopy be used whenever possible.

Introduction

Tympanic membrane (TM) perforations--which can be caused by suppurative otitis media, trauma, middle ear tumors, and iatrogenic injuries--appear in a variety of sizes, shapes, and sites. The size of a TM perforation in affected patients is closely related to the degree of hearing loss and sound transmission across the middle ear cleft. (12) The size and other characteristics of TM perforations usually determine the nature and degree of clinical signs and symptoms at presentation. For example, perforations located along the edges of the TM are believed to be associated with more complications than those that are centrally located. (3,4)

While some perforated TMs heal spontaneously, others persist and require treatment. And just as the specific features of a particular perforation determine its presentation, so do theyhave an impact on its management and outcome--particularly size. (5) For example, it is known that tympanoplasty failure rates are higher in patients who have larger perforations. (6) Also, hearing aids are less beneficial in patients with large perforations. (7)

In most cases, otologists evaluate size, shape, and site by simply looking through a handheld otoscope. In other cases, we use an operating microscope. But while these methods are usually sufficient to characterize shape and site, they are not as precise in approximating size as a percentage of the total area of the TM. The accuracy of estimating size by standard otoscopy is limited not only by interobserver errors but by the fact that most perforations are not uniformly round. Thus, their area is not easy to gauge by simple observation or to calculate on the basis of the TM diameter.

The development of computer-based video-otoscopy systems that precisely calculate the size of a perforation relative to the size of the TM has obviated many of these problems. (8-11) These systems are accurate and their measurements are reproducible. As such, they provide a standard against which we can measure the accuracy of subjective estimates made by otolaryngologists.

Subjects and methods

This prospective study was conducted between Dec. 1, 2005, and Nov. 27, 2006. The subjects of this study were 6 ENT specialists; from highest rank to lowest, they included 2 Consultant Surgeons (O.G.B.N., A.A.A, and later P.A.O.), 2 Senior Registrars (T.S.I. and D.D.K.), and 2 Registrars (H.O.L. and P.O.O.), all of whom were randomly selected from among their colleagues at our institution. All 6 specialists had undergone an eye test prior to the study, and their vision was certified as normal in all cases. Each specialist independently examined 100 TM perforations in 76 patients (52 unilateral perforations and 24 bilateral).

After all 6 observers had subjectively estimated the size of a particular perforation, the eardrum was then assessed objectively by video-otoscopy (CompacVideo Otoscope, models 23120 [NTSC] and 23120P [PAL]; Welch Allyn; Skaneateles Falls, N.Y.). All images were adapted through a Cute!TV USB driver (model 03020701 ;VV mer Technology Corp.; Taipei, Taiwan) and recorded on a computer (Inspiron 600M with Pentium M processor; Dell; Round Rock, Tex.). The ImageJ image-processing program (version 1.35j; National Institutes of Health; Bethesda, Md.) was used to calculate the area of the perforation (figure 1). Comparative analysis and statistical significance were tested with Statistical Package for the Social Sciences software (version 11; SPSS; Chicago).

Ethical clearance was granted by the University of Ibadan/University College Hospital Institution Review Committee, and informed consent was obtained from all patients.

Results

The sizes of the perforations expressed as a percentage of the total area of the TM as calculated by video-otoscopy varied greatly--from 0.9 to 98% (mean: 44.09%) (table 1). Overall, the video-otoscopic calculations revealed that each group of specialists significantly overestimated the sizes of the perforations (p < 0.01). Although the Consultants and the Senior Registrars were significantly more accurate than the Registrars (p < 0.01 and p= 0.02, respectively) (table 2), they were still significantly less accurate than video-otoscopy (figure 2).

Discussion

In this study, greater clinical experience was correlated with greater accuracy in visually estimating the size of TM perforations, even though the difference between the findings of the Consultants and the Senior Registrars was not statistically significant. The Consultants' estimates were closest to the video-otoscopic calculations, and the estimates of the Senior Registrars were more accurate than those of the Registrars. Still, even the Consultants' estimates were at significant variance with the video-otoscopic calculations (p < 0.01). Our findings in this regard were similar to those reported by Hsu et al (11) and Hampal et a1. (12) In those two studies, the differences between visual estimates and video-otoscopic calculations were also statistically significant (p < 0.01 in both studies).

[FIGURE 1 OMITTED]

Our findings do conflict with the study by Hsu et al (11) in one respect. They found that Residents were more accurate than Consultants. However, they made no mention of the vision status of the assessors in the methodology section of their report. Such an omission might be relevant because, of course, most Consultants are older than residents and more likely to be affected by presbyopia. In our study, we obviated this possibly militating factor by ensuring that all the ENT specialists had good vision.

[FIGURE 2 OMITTED]

We conclude that visual estimation of the size of TM perforations is inaccurate. We recommend that video-otoscopy be used for this purpose whenever possible.

Acknowledgments

We thank the Consultant Surgeons in the Department of Otorhinolaryngology at University College Hospital in Ibadan for recruiting the patients used in this study. We also thank the staff of the Department of Ophthalmology for helping us with screening the vision of the ENT specialists. Finally, we thank Dr. Emmanuel Orimadegun for performing the statistical analysis.

References

(1.) Mehta RP, Rosowski JJ, Voss SE, et al. Determinants of hearing loss in perforations of the tympanic membrane. Otol Neurotol 2006; 27(2):136-43.

(2.) Voss SE, Rosowski JJ, Merchant SN, Peake WT. How do tympanicmembrane perforations affect human middle-ear sound transmission? Acta Otolaryngol 2001; 121 (2): 169-73.

(3.) Schraff S,Dash N, Strasnick B. "Window shade" tympanoplasty for anterior marginal perforations. Laryngoscope 2005;115(9):1655-9.

(4.) Ibekwe TS, Ijaduola GT, Nwaorgu OG. Tympanic membrane perforation among adults in West Africa. Otol Neurotol 2007;28 (3):348-52.

(5.) Angeli SI, Kulak JL, Guzman J. Lateral tympanoplasty for total or near-total perforation: Prognostic factors. Laryngoscope 2006;116 (9):1594-9.

(6.) Fadl FA. Outcome of type-1 tympanoplasty. Saudi Med J 2003;24 (1):58-61.

(7.) Martin HC, Munro KJ, Lam MC. Perforation of the tympanic membrane and its effect on the real-ear-to-coupler difference acoustic transform function. Br J Audiol 2001;35(4):259-64.

(8.) Jones WS. Video otoscopy: Bringing otoscopy out of the "black box." Int J Pediatr Otorhinolaryngol 2006;70(11): 1875-83.

(9.) Sullivan RF.Video otoscopyin audiologic practice. J Am Acad-Audiol 1997;8(6):447-67.

(10.) Patricoski C, Kokesh J, Ferguson AS, et al. A comparison of in-person examination and video otoscope imaging for tympanostomy tube follow-up. Telemed J E Health 2003;9(4):331-44.

(11.) Hsu CY, Chen YS, Hwang JH, Liu TC. A computer program to calculate the size of tympanic membrane perforations. Clin Otolaryngol Allied Sci 2004;29(4):340-2.

(12.) Hampal S, Padgham N, Bunt S, Wright A. Errors in the assessment of tympanic membrane perforations. Clin Otolaryngol Allied Sci 1993;18(1):58-62.
Table 1. ENT specialists' estimates of TM size relative to the
video-otoscopic findings

                                          Difference in    Paired
Evaluator            Range (mean) (%)     the mean (%)     t test

Video-otoscope      0.9 to 98.0 (44.09)        --            --
Consultants         1.5 to 96.5 (51.62)        7.53       p < 0.01
Senior Registrars   1.5 to 97.5 (52.91)        8.82       p < 0.01
Registrars          3.0 to 96.0 (56.09)       12.00       p < 0.01

Table 2. Statistical significance of differences in accuracy
among the three groups of specialists

Comparison                          Paired t test

Consultants vs. Senior Registrars     p = 0.175
Consultants vs. Registrars            p < 0.01
Senior Registrars vs. Registrars      p = 0.02
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Title Annotation:ORIGINAL ARTICLE
Author:Ibekwe, Titus S.; Nwaorgu, Onyekwere G.B.; Adeosun, Aderemi A.; Kokong, Daniel D.; Lawal, Hakeem O.;
Publication:Ear, Nose and Throat Journal
Article Type:Clinical report
Geographic Code:1USA
Date:Oct 1, 2008
Words:1442
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