3Belfast, Glasgow, and AAO-HNS Reporting Standards

FWhy we need reporting standards

For most of the twentieth century, surgeons reported the results of middle-ear surgery however they pleased. One series averaged hearing at three frequencies, another at four; one measured success as any improvement in air conduction, another as closure of the air–bone gap (ABG)to within 10, 20 or 30 dB; some used the better pre-operative bone line, others the post-operative one. The consequence was that two papers reporting the same operation could quote wildly different “success rates,” and no reader could compare them. Reporting standards exist to fix exactly this: to make the numbers from different units, different prostheses and different decades mean the same thing so they can be compared fairly [1995].

Three landmarks dominate the field, and this module is about all three. The AAO-HNS Committee on Hearing and Equilibrium guideline of 1995 standardised howhearing is measured and presented — which frequencies, which gap, which graph [1995]. The Belfast Rule of Thumb and the Glasgow Benefit Plot, both from the British Isles, tackled a deeper problem: a closed air–bone gap in one ear does not necessarily mean the patient hears any better in everyday, two-eared life [1985, 1991]. Together they separate three distinct questions — was the gap closed?, is the operated ear now usable?, and does the patient actually benefit?— that careless reporting blurs into one.

FThe AAO-HNS minimal reporting guideline

The 1995 guideline from the American Academy of Otolaryngology–Head and Neck Surgery is the backbone of modern outcome reporting for conductive hearing loss [1995]. Its rules are deliberately mechanical, because the whole point is to remove the freedom that made old series incomparable. The essentials a trainee must know are:

• Four-frequency pure-tone average. Thresholds are averaged at 0.5, 1, 2 and 3 kHz. The committee deliberately substituted 3 kHz for the older 4 kHz so the average sits closer to the speech range that matters to patients.
• Air–bone gap is the primary conductive outcome. Because ossiculoplasty repairs the conductive mechanism, success is judged by the gap between air and bone conduction, not by air conduction alone.
• Same-session bone conduction. The gap must be computed from the pre- and post-operative bone line measured at the same sitting as the air line, so the gap is internally consistent rather than borrowing an old bone threshold.
• Individual data in a scattergram.Series should plot every patient’s pre- versus post-operative gap, not merely quote a mean, so the full distribution — including failures and outliers — is visible.

The guideline also requires honest handling of the bone line. If bone-conduction thresholds improve after surgery — overclosure, usually an artefact of removing a mass-loaded or fixed ossicular chain — that improvement must be reported transparently rather than used to inflate the apparent gap closure. The familiar shorthand that an operation is a “success” when the post-operative gap is within 20 dB is consistent with this framework, but the guideline’s real contribution is the method, not any single threshold [1994].

TThe Belfast Rule of Thumb

The Belfast Rule of Thumb grew out of an uncomfortable observation. In 1985, Gordon Smyth and the statistician Colin Patterson at the Royal Victoria Hospital in Belfast correlated 203 patients’ own assessment of their hearing after middle-ear reconstruction with the audiometric data from bothears. The strongest predictor of whether a patient felt they had benefited was not the air–bone gap closure at all, but the final air-conduction hearing level of the operated ear relative to the other ear [1985]. A perfectly closed gap could leave a patient unimpressed if the operated ear was still much worse than its fellow.

From this came the simple, memorable 15/30 dB rule: a patient is likely to perceive a genuine benefit if the operated ear ends up within 15 dB of the non-operated ear, or if its air-conduction threshold is 30 dB or better. The reasoning is physiological. When an ear is more than 30 dB down and more than 15 dB poorer than its partner, the auditory system tends to ignorethe worse ear and the patient lives on the better one — so improving the poor ear, even substantially, changes little in real life. The explorer below applies the rule live: move the two thresholds and watch the verdict flip.

The rule’s great virtue is that it reframes a monaural number as a binaural, patient-centred judgement, and it does so in a sentence any clinician can apply at the microscope or in clinic. Its weaknesses are equally clear. It is all-or-none: an ear that improves from 60 to 35 dB scores no “benefit” even though the gain is real and may matter when the better ear later deteriorates. It does not gradepartial improvement, and it says nothing about the gap itself. In one applied series, the rule agreed with patients’ own assessment of benefit in about 73% of chronic otitis media ears, performing better in mucosal than in squamosal disease [2023]. It is best used alongsidethe air–bone gap, not instead of it.

TThe Glasgow Benefit Plot

Where Belfast gives a rule, Glasgow gives a picture. In 1991 Browning, Gatehouse and Swan published the Glasgow Benefit Plot, a graph built from the same insight: because listening is binaural and disability is dictated by the better-hearing ear— usually the non-operated one — what matters is the relationship between the two ears before and after surgery [1991]. The plot puts the operated-ear air-conduction threshold on one axis and the other ear on the other, with reference lines at the 30 dB level that separates socially adequate from inadequate hearing, and a diagonal of equality where the operated ear becomes the better ear.

Each patient appears as a point that moves from its pre-operative to its post-operative position, and the direction of travel reveals the benefit at a glance. An ear that was already much worse than its partner and merely improves without crossing the 30 dB line or the diagonal has gained little in binauralterms, however much its gap closed — the prototypical “technical success, no perceived benefit.” An ear that crosses into the socially adequate zone, or overtakes its partner to become the better ear, has produced a benefit the patient will genuinely notice. Because it displays every patient individually and predicts as well as reports, the plot doubles as a counselling and prognostic tool: it can show a patient before surgery roughly where their ear is likely to land [2007].

CChoosing and combining the methods

These three standards are not rivals; they answer different questions and are strongest in combination. The AAO-HNS air–bone gap tells you whether you repaired the mechanism— the surgeon’s technical endpoint, and the only one that lets you compare your prostheses and techniques against the literature. The Belfast Rule and the Glasgow Plot tell you whether the patient benefited, which is the endpoint that justifies the operation. A unilateral, much-worse ear can close its gap beautifully (AAO-HNS success) and yet sit in a no-benefit zone on the Glasgow Plot and fail the Belfast Rule, because the good contralateral ear was carrying the patient all along [2005].

The comparison below illustrates the divergence: binaural methods track what patients actually report far more closely than gap closure alone, which is inherently monaural.

The practical implications for everyday decision-making are concrete. Reporting onlythe air–bone gap flatters surgery of the worse ear and can justify operations that give the patient nothing audible; reporting only a binaural rule hides whether your reconstruction technique is sound. For consent and counselling, the binaural framing is the honest one: a patient with one good ear should be told plainly that closing the gap in the worse ear may not change their day-to-day hearing — a conversation the Glasgow Plot makes visual. For audit and publication, the AAO-HNS scattergram is indispensable. Mature outcome reporting carries both.

CReporting a series honestly

When you write up or audit a series of ossiculoplasties, a few disciplines keep the figures honest and comparable. State the pure-tone average frequenciesexplicitly — ideally the AAO-HNS 0.5/1/2/3 kHz — because a four-frequency average that includes 4 kHz, or a three-frequency speech average, will not match the guideline and must be labelled as such. Compute the gap from same-session bone conduction. Publish a scattergram of individual pre- versus post-operative gaps rather than a lone mean, so the distribution and the failures are visible [1995]. Declare any overclosure rather than letting it inflate the gap closure.

Finally, report the follow-up interval and avoid quoting only the earliest, most flattering audiogram, since conductive results drift over time. A defensible paper or logbook gives the AAO-HNS gap distribution anda binaural benefit measure, names its frequencies and its time point, and lets the reader see every patient. Do that, and your numbers will mean the same thing to a reader in another country and another decade — which is the entire purpose these standards were created to serve [1991, 1985].