Procedures
This is an open-labelled randomized controlled trial involving two groups which are FFVT vs FFCT (digital hand-held device). The app is designed by our team using the Flutter-Dart programming tool and the speaker is produced via hand-held devices of Apple and Android brands. Two types of sound were created which represent the individual sounds from FFVT, which are soft sounds (whisper) ranging from 30-40dB and loud sounds (conversation voice) ranging from 60-70dB. These click sounds range from 500-3000 Hz, which corresponds to the standard pure-tone average values. Calibration of sounds produced from the mobile app was done using an audiometer at distances of 60 cm and 15 cm. The tests were all done in a soundproof room.
The examiner initially stands at a distance of 60 cm (full arm’s length) behind a seated patient to prevent lip reading. The patient’s eyes were shielded and tragal rubbing of the non-test ear was performed. For FFVT, a sequence of spondee/bisyllable words was whispered and the patient repeats it. If the patient fails to hear the whispered words at 60 cm, the examiner then moves closer to 15 cm (half arm’s length) and whispers the spondee words again. If no response is obtained, conversational voice at 60 cm and lastly conversational voice at 15 cm distances are used if the patient is still unable to hear .11 For each distance, the words were repeated thrice and a different set of Spondee words was used. The patient’s hearing threshold was the voice and distance level at which more than 50% of words were repeated correctly. [Figure 1]
The same technique was conducted for FFCT but, instead of whispering, we used the soft and loud sounds from the mobile app [Figure 1 & 2]. The distances used were also similar to FFVT, with 60 cm initially and then moving closer to 15 cm. The sounds were produced 3 times, with 2 out of 3 answers were considered as the patient’s hearing threshold.
Sample size calculation
The sample size was determined by using a power study via a web-based sample size calculator(https://clincalc.com/stats/samplesize.aspx). The sample size calculation was based on the reference data from the National ORL registry of hearing-related diseases in 2011.12 We estimated that we would expect 86% sensitivity and 90% specificity while performing the FFVT. Hence, we have considered a 90% power and 5% marginal error, which leads to a minimum sample size of 25 patients/50 ears per group. Randomization was done using a web-based randomizer:http://www.graphpad.com/quickcalcs/randomize1@ 7th December 2019@1500H . The total number of patients was separated into 2 groups and each group contained 25 samples (50 ears). The numbers were randomized and printed according to the web-based randomizer at the aforementioned date and time. Generated numbers are then saved for further reference.
Statistical Analysis Plan
Based on the studies reported by Malaysian National Otorhinolaryngology of Hearing-related Diseases,12 the prevalence of hearing impairment was reported to be approximately 50%, and thus, we estimated that we would expect an 86% sensitivity and 90% specificity while performing a free field voice test.8,13Descriptive data were expressed as mean ± standard deviation (SD) unless otherwise stated. Categorical data were analyzed using Chi-square test while, non-categorical data were calculated using Student t-test.A value of P < 0.05 was considered statistically significant. The data collected were analyzed using an intention-to-treat basis.
RESULTS
1.3.1 Demographic details
The minimum age of participants was 18 years old while, the maximum age was 80 years old. 52% of the participants were male and 62% came with the complaint of unilateral hearing loss. 40% of our participants had no additional symptoms besides the main complaint of hearing loss. 33% of participants had tinnitus, 11% had associated vertigo or giddiness while 5% had otorrhea. Other additional symptoms like rhinitis, otalgia, headache and facial weakness were reported to be less than 5%. 45% of participants had normal hearing when PTA was performed. 28% of participants had mild hearing loss, 17% had moderate hearing loss and severe hearing loss had 9% of participants. Only 1% had profound hearing loss. FFCT took an average of 1 minute to be completed for 60% participants. FFVT took an average of 2-3 minutes.