Incidence of indications for tonsillectomy and frequency of evidence-based surgery: a 12-year retrospective cohort study of primary care electronic records (2024)

Data source and study cohort

This is a retrospective open cohort study of children aged 0–15 years registered with a general practice contributing to The Health Improvement Network (THIN). THIN is a database of anonymised patient records from >700 UK general practices. It contains information on diagnoses, symptoms, referrals to secondary care, tests, and treatments in primary care.²⁷ It is broadly generalisable to the UK population in terms of demographics and medical condition prevalence.^28,29

The researchers had complete access to the full THIN database. Data were only included after the date of practice acceptable mortality reporting. This is the date after which patient deregistrations in each practice were recorded consistently, ensuring that the denominator, the registered population, was accurate.³⁰ Children were eligible for inclusion from birth, or if not registered with a THIN practice from birth, then registered for at least 3 years before entry. This allows sufficient time to meet the evidence-based criteria for tonsillectomy. The earliest year of entry to the cohort was set at 2000.

Children who had a tonsillectomy before entry in the cohort were excluded. Patients were followed up until the earliest of the following dates: age 16 years, death, leaving the practice (deregistration), last data extraction from the practice, or tonsillectomy.

Exposures

Potential indications for tonsillectomy were identified from clinical coded consultations for sore throat episodes, tonsillar neoplasia, PFAPA, peritonsillar abscess, sleep apnoea, other sleep disordered breathing, glomerulonephritis, and guttate and chronic plaque psoriasis. As it is difficult to distinguish new sore throat episodes from ongoing episodes, a pragmatic decision was taken to consider as a new episode any consultation for sore throat (including pharyngitis, tonsillitis, throat infection, or sore throat symptoms) at least 14 days after the previous consultation. Code lists are available from the authors on request. Patients were categorised according to potential indications for tonsillectomy.

In initial analysis, the authors were unable to identify any potential indications for some patients who underwent tonsillectomy. This may have occurred because some consultations for sore throats were recorded using a less specific code, such as another upper respiratory tract infection (URTI). The authors therefore broadened the definition of a sore throat consultation to include any consultations with a clinical code for URTI or otitis media. They also conducted a sensitivity analysis, including in their counts of sore throat episodes any consultations where no code for URTI was used but an oral antibiotic commonly used for sore throat (penicillin V, erythromycin, or clarithromycin) was prescribed.

Outcome

The main outcome of interest was tonsillectomy or adenotonsillectomy.

Statistical analysis

Annual incidence of indications for tonsillectomy

Sore throat consultations declined between 2005 and 2016. Incidence of sore throats meeting Paradise criteria (98.0% of evidence-based indications) was 28% lower in 2016 than in 2005 (Table 1). Similarly, consultations for five to six sore throats in a year fell by 27%; for three to four recurrent sore throats by 22%; for two to three sore throats by 19%; and by 13% for a single sore throat. Consultations for peritonsillar abscess also fell by 39%. In contrast, consultations for sleep apnoea rose 48% from 2005 to 2016, and those for sleep disordered breathing increased by 2% (not shown in Table 1, information available from authors on request).

Between 2005 and 2016, the average annual incidence of meeting at least one evidence-based indication for tonsillectomy in children was 4.2 per 1000 person–years. A much larger number of children consulted with other potential indications for tonsillectomy that did not meet evidence-based criteria, particularly with one, two, or three to four sore throats in a year (Table 2).

Frequency of tonsillectomy in children with indications

In all, 13.6% (2144/15 760) of children with an evidence-based indication underwent tonsillectomy. Likelihood of undergoing tonsillectomy increased with frequency of sore throat consultations in a single year — 3.2% (5503/170 687) with three to four sore throats, 8.9% (2266/25 420) with five to six annual sore throats, and 13.9% (2129/15 320) of those meeting Paradise criteria.

The vast majority of children consulting with recurrent sore throats did not undergo tonsillectomy; however, the small proportion that did accounted for most tonsillectomies (Figure 1). The indications most likely to be followed by tonsillectomy were sleep apnoea, 22.2% (706/3185), followed by peritonsillar abscess, 14.8% (100/675), and sleep disordered breathing, 14.8% (2246/15 205) (Table 2).

Annual incidence of tonsillectomy

The crude annual incidence of tonsillectomy was 2.5 per 1000 person–years. It followed a broadly similar pattern to the incidence of indications, declining from 2005 to 2011 and then remaining relatively stable (Table 1). Age adjustment had little effect on trends or rates. Annual English hospital-reported tonsillectomy rates showed the same temporal pattern as the authors’ primary care data.

Indications for tonsillectomies undertaken from 2005 to 2016

From 2005 to 2016, 11.7% (2144/18 281) of tonsillectomies had evidence-based indications; 99.3% of these met the Paradise criteria. Tonsillectomies without an evidence base were mainly for sore throats: five to six (12.4%), two to four (44.7%), or one (9.9%) within a single year. In addition, 3.9% were for sleep apnoea, and 12.3% for other sleep disordered breathing.

The proportion of tonsillectomies attributable to Paradise criteria, five or six annual sore throats, or to other sleep disordered breathing changed little. The proportion attributable to obstructive sleep apnoea increased fourfold, from 1.2% to 5.5% (Figure 2).

Summary

About four in 1000 children met evidence-based criteria for tonsillectomy annually between 2005 and 2016. The vast majority had recurrent sore throat consultations meeting Paradise criteria. Fewer than one in seven underwent surgery.

Two or three children in 1000 underwent tonsillectomy annually between 2005 and 2016. Fewer than one in eight had evidence-based indications. The proportion did not change over 12 years. In the UK, 32 500 of the 37 000 childhood tonsillectomies in 2016–2017 were therefore unnecessary.^2,6 Most (54.5%) tonsillectomies were carried out on the very large numbers of children who consulted with one to four sore throats in a year, but the vast majority of these children do not undergo or require tonsillectomy. The mismatch between children meeting evidence-based criteria and those undergoing tonsillectomy is shown in Figure 3.

Strengths and limitations

The authors’ findings are obtained from a very large dataset reflecting current UK clinical practice over 12 years and capture both free NHS and private tonsillectomies. The tonsillectomy rates correlated closely with childhood tonsillectomy rates reported in England Hospital Episode Statistics (r = 0.896).

The authors identified likely indications for 95.2% of tonsillectomies from clinically coded consultations. Consultations in primary care are 15 times more common than in emergency departments, and upper respiratory infections are uncommon in the latter; therefore, primary care records will miss few relevant consultations.^32,33

Paradise criteria require specific documentation of sore throats and their clinical features. The authors’ broad (sensitive) definition of a sore throat, counting any URTI consultation as a sore throat episode, may overestimate the frequency of evidence-based indications. In sensitivity analyses they investigated the effect of using an even broader (more sensitive) definition to include any consultation without a clinical code where antibiotics consistent with a sore throat episode were prescribed (penicillin V, erythromycin, or clarithromycin). This increased the number of evidence-based tonsillectomies to 17.5%. The authors then used a narrower (more specific) definition of a sore throat, including only those clinically coded as sore throat episodes. This reduced the proportion of evidence-based tonsillectomies to 4.4%, reduced the proportion of tonsillectomies attributable to sore throat to 70.9%, and increased the proportion without an identifiable indication to 11.1%. In all scenarios, only a minority of tonsillectomies were evidence-based and, even with the narrowest definition of sore throat, only a minority (32.0%) of children meeting Paradise criteria underwent tonsillectomy.

For sore throat-related indications the authors initially intended to consider tonsillectomy to be indicated for only 1 year after the patient last consulted for the indication. But median time from indication to tonsillectomy was 356 days, and applying a 1-year time limit for indications meant the authors were unable to identify any indications for an additional 13% of tonsillectomies. Therefore, they identified the best ever indication rather than indications within 1 year before tonsillectomy: this may overestimate the frequency of evidence-based indications.

Some may consider there is sufficient evidence to support tonsillectomy for other indications. Children affected by recurrent otitis media may benefit modestly from adenotonsillectomy, although it is unclear if tonsillectomy adds to the benefits of adenoidectomy.³⁴ Tonsillectomy may be beneficial for sleep apnoea confirmed by polysomnography in 5–9 year olds, for peritonsillar abscess, or for psoriasis.^19,20,25 Others conclude the evidence does not support tonsillectomy in PFAPA.³⁵ But a combination of evidence-based indications, or breathing-related indications, or peritonsillar abscess, accounts for only 28.4% of tonsillectomies. Furthermore, most children with any of these indications do not undergo tonsillectomy. Using a broader definition of eligibility for treatment increases the proportion of tonsillectomies that can be considered indicated, but decreases the proportion of eligible children who undergo surgery.

Comparison with existing literature

This is the first ever study to estimate the incidence of evidence-based indications for tonsillectomy in children and the proportion of affected children who undergo the procedure. It is the first study to comprehensively estimate the proportion of tonsillectomies that are evidence-based. A study in 23 self-selected UK general practices found one-quarter of 237 tonsillectomies in the late 1990s met evidence-based criteria.³⁶ A larger analysis suggested <1% of tonsillectomy patients in 2008 met Paradise criteria.³⁷ However, this study probably underestimated eligibility as it required sore throats to be precisely coded in general practice records.

Although others report rising hospital admissions for peritonsillar abscess, the authors of the current study found primary care consultations for peritonsillar abscess and for recurrent sore throat consistently declined over the same period.³⁸ This suggests a changing pattern of presentation rather than an increase in incidence.

The authors found UK tonsillectomy rates changed little from 2005 to 2016, with a slight decline in the years to 2011, followed by a modest increase. By comparison, in Germany, childhood tonsillectomy rates decreased by 17.3% from 2010 to 2013, but rates remain twice those in the UK.³⁹ The authors found an increasing propensity for sleep apnoea consultations to result in tonsillectomy: sleep apnoea consultations increased by about half, but tonsillectomies for obstructive sleep apnoea increased fourfold. Overall, the authors’ attribution of indications for childhood tonsillectomy — 78.5% sore throat, 16.2% obstructive symptoms, and 0.5% peritonsillar abscess — is comparable to a national UK audit which found 83.3%, 14.7%, and 0.4%, respectively.¹⁰ Fewer tonsillectomies could be attributed to sleep apnoea than the 25% suggested by UK professional bodies,⁴⁰ or the two-thirds reported from the US.^41,42

The authors found guideline discordant (overtreatment alongside possible undertreatment) clinical management of recurrent sore throat in the UK to be stable over many years. Overtreatment is an increasingly recognised phenomenon.^43,44 Guideline discordant clinical management has been observed in relation to both statins and depression, and in the US has increased in relation to back pain and headache.^45–48

Implications for research and practice

The results of current trials of tonsillectomy for obstructive sleep disordered breathing are awaited.^22–24 High quality randomised controlled trials are also needed to evaluate tonsillectomy for peritonsillar abscess, guttate, and chronic plaque psoriasis. The frequency of indications for tonsillectomy and evidence-based tonsillectomies should be investigated in countries with higher and lower tonsillectomy rates than the UK.

These findings have some practical implications for UK clinical practice. Because they are undertaken on children who do not benefit, most tonsillectomies may cause more harm than good. This is ethically dubious and not a good use of resources. Most children meeting evidence-based criteria do not undergo tonsillectomy. Therefore, it cannot be considered a necessity. Doctors should already be informing parents of the likely effectiveness of tonsillectomy, and should now also inform them that most children with either recurrent sore throats or sleep apnoea do not undergo tonsillectomy and have no need to.

Funding

Professor Tom Marshall is partly funded by the National Institute for Health Research (NIHR) through the Collaborations for Leadership in Applied Health Research and Care for West Midlands (CLAHRC-WM). The views expressed in this publication are not necessarily those of the NIHR, the Department of Health, NHS partner trusts, the University of Birmingham, or of CLAHRC-WM.

Ethical approval

All research using anonymised patient records from THIN had prior approval from the NHS South-East Multi-Centre Research Ethics Committee subject to independent scientific review. This study received THIN Scientific Review Committee approval (reference 15-003).

Provenance

Freely submitted; externally peer reviewed.

Competing interests

The authors have declared no competing interests.

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