Screening for otitis media with effusion to measure its prevalence in Chinese children in Hong Kong.

Abstract

In an attempt to gain a better understanding of the prevalence of otitis media with effusion (OME) in the Hong Kong community, and to compare the characteristics the disease here with OME as it is described in the Western literature, we screened more than 6,000 6- and 7-year-old children with both clinical and audiologic examinations. The initial positive screening rate was 5.3%. Upon further evaluation, we determined that the overall prevalence of persistent OME was 2.2%. We found that the disease pattern and natural history of persistent OME in Hong Kong children are similar to those reported in the Western literature.

Introduction

Otitis media was documented in very early Chinese literature. [1-3] In Huang Di Nei Jing (Internal Medicine of the Yellow Emperor), which was written circa 1900 BC, there appeared a description of hearing problems that were related to both blockage of the internal drainage and changes in the weather. A similar description was made in Ren Ji Zhi Zhi Fang (The Prescription of Benevolence), written during the Song dynasty (960-1279 AD); translated, it reads, "There is fluid in the ear cavity. If it is mild, it will not harm; if it is associated with wind and heat, the fluid becomes more viscous and blocks the ear, causing hearing loss." Another description appeared in Zheng Zhi Zhun Sheng (Precise Diagnosis and Prescription), published during the Ming dynasty (1368-1644 AD): "There is a kind of ear disease that does not discharge nor show any swelling externally, but blocks the ears."

Otitis media with effusion (OME) is the most common indication for elective surgery for children in the West. The annual cost of this care is roughly $2 billion in the United States and [pound]50 million in the United Kingdom. [4] Despite the long history of Chinese medicine, specialists and epidemiologists know little about the epidemiology of OME in Chinese children. During the 1960s, a report in a Chinese textbook cited prevalence rates of 2.8 to 16.8% in Nanjing and Chungqing. [5] In Hong Kong, where more than 90% of the population is Chinese, we were struck by the apparent scarcity of new cases referred to us from the primary healthcare system. The occurrence of OME among Caucasian children in Hong Kong appears to be consistent with that reported in other centers worldwide. [6]

The apparent low incidence of OME among Chinese children in Hong Kong led us to wonder if a large number of cases was being overlooked. To find out, we designed and conducted a screening program and a followup study of identified cases to better understand the scope of the problem and perhaps to gain some insight into the etiology of OME in Hong Kong. We believed that the information we gathered would help us determine whether the disease profile in Hong Kong is different from that in the West. Also, it might lead us to improve the lives of a large number of children whose disease is undetected. Children with persistent OME are known to have more learning difficulties and poorer social skills than nonaffected children, and studies have confirmed the negative impact that a moderate hearing loss has on a child's cognitive development. [7-9]

Materials and methods

The objectives of this study were to determine the prevalence of OME among Chinese school children aged 6 and 7 years in Hong Kong. We performed a nested case control analysis and a followup study of the natural course of the disease in diagnosed patients.

Our target population consisted of school children who were attending primary one class in Hong Kong. From among the 1,094 schools that were registered with the Education Department, we randomly selected 80 (although we ensured that all districts were represented). We obtained permission from school principals to screen pupils on a particular date between November 1995 and March 1996 or between November 1996 and March 1997. Our final analysis included only 6- and 7-year-old children of Chinese descent. Prior to screening, we also obtained parental consent. Parents who agreed to the screening provided a brief medical history (via questionnaire) of their children.

During the initial screening phase of our study, all eligible children underwent an otoscopic examination and 226-Hz tympanometry on the school premises; these activities were performed by an otolaryngologist and an audiologist, respectively. All children who had type B or type C tympanograms (Fiellau-Nikolajsen's modified Jerger's nomenclature [10]) with no stapedial reflex (unilateral or bilateral) were scheduled for a followup appointment at the specialist clinic within 3 weeks of the screening.

At the specialist clinic, we obtained a detailed history on each child. Each child also underwent a tuning-fork test, examination under microscopy, repeat tympanometry, stapedial reflex test, and pure-tone audiometry. A diagnosis of persistent OME was pronounced for those children who exhibited effusion on microscopy or an abnormal tympanometry with an average air-bone gap of 10 dB. We included in a separate analysis those children who had acute otitis media or any other concurrent ear disease, a history of ear surgery, or any craniofacial anomalies (e.g., cleft palate) and those who fell outside the age range. We also screened children who were not of Chinese descent, but we did not include them in this study.

Those children in whom persistent OME was confirmed at the specialist clinic were entered into a longitudinal study for 6 months. They underwent repeat testing at months 1, 2, and 6. No antibiotic was prescribed, and the only medical treatment given was to control symptoms such as allergic rhinitis.

Results

Prevalence study. Of the 6,752 children who were enrolled in the 80 selected schools, 6,070 participated in the screening (89.9%); of the remainder, 591 had refused screening (8.8%), and 91 had been absent from school on the day of screening (1.3%). Of all the students screened, 172 were excluded from our analysis (but were not denied further evaluation or treatment) because they were either outside the age range or not of Chinese descent. That left 5,898 children available to serve as the base population for a calculation of prevalence.

Of the 6,070 pupils who were examined, 459 had positive screens (7.6%). Almost all of them (446) kept their appointment at the specialist clinic for further assessment. Again, seven children were excluded from this study because they were either too old or too young, six were excluded because they were not of Chinese descent, and seven who had a cleft palate were considered separately. Thus, we had 439 eligible positive screens among the 5,898 eligible screens, for a positive screening rate of 7.4%. From there, we excluded 126 children whose flat tympanograms were attributed to ear canal blockage by wax. All told, 313 of the 5,898 children were initially diagnosed with OME on the school premises by specialist otoscopy and tympanometry, for a prevalence of 5.3%.

During followup at the specialist clinic, 128 of the 313 children were found to actually have persistent OME, for an overall prevalence of 2.2% (128/5,898); 41 of the 128 children (32.0%) had unilateral OME and 87(68.0%) had bilateral disease.

Longitudinal study. The 128 children who had confirmed OME were scheduled for re-examination at 1, 2, and 6 months after their initial visit to the specialist clinic. Of the 94 patients who returned for the 6-month visit, 30 (32.0%) still had OME. Their parents were advised that these children should undergo myringotomy and insertion of ventilation tubes, and 10 did so within the subsequent 6 months.

Discussion

Our overall OME prevalence of 5.3% found by screening tympanometry and otoscopy in 6-and 7-year-old children is similar to a figure reported from Japan (4.3%), [11] but lower than one from Denmark (9%). [12] A similar study of 7-year-olds in Finland found a positive initial screening prevalence of 4.2% and a confirmed diagnosis rate of 2.9%. [13] Again, these figures are similar to our own of 5.3 and 2.2%, respectively. In a review of OME, Daly reported wide variations in prevalence (range: 3-17%) among children aged 5 to 8 years; many different methodologies and definitions were used in the studies he reviewed. [14]

Evidence derived from our study suggests that the prevalence of OME among Chinese school children is higher than generally believed. In fact, 88% of the confirmed cases had not been diagnosed prior to our screening program. By contrast, a study in Sweden reported that one-half of the cases of OME detected by screening had already been diagnosed [15]

In our study, 32% of cases resolved spontaneously within 6 months, a figure that is comparable to the 24% rate of spontaneous resolution reported in a cohort group of 7-year-olds in Denmark. [16] Although there have been reports of much higher resolution rates-as high as 67% within 1 month in one study[17]-our methodology was different in that we regarded changes in tympanometry within 3 weeks as indicative of an episode of acute otitis media, with or without effusion. Such a methodology has been employed by Senturia et al and others. [18]

In 1998, we reported that some parameters observed at the time of the initial diagnosis might be predictors of outcome over 6 months. [19] Some of these unfavorable parameters were a type B tympanogram, an opaque or amber tympanic membrane, fluid found on microscopy, and a hearing loss greater than 20 dB at the initial examination.

Our study strongly suggests that the prevalence and natural history of OME in Chinese school children in Hong Kong is not different from that in the West. We have identified a notable prevalence of OME in Hong Kong, but the general public is largely unaware of the condition's existence. Identifying OME in early childhood is not an easy task, even for specialists. Our study provides the only real insight into the nature of this problem for our local health authorities and medical professionals.

From the Division of Otorhinolaryngology, Department of Surgery, Prince of Wales Hospital, The Chinese University of Hong Kong.

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