This atlas domain was last updated in 2016.

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In reporting these rates, the intention is to question where there is significant variation, whether or not this variation is warranted and is variation based on genuine differences between populations or whether other factors are at play.

The ideal intervention rate for both procedures is not known.

Updated March 2016

This Atlas domain has been updated to show data for 2009–10 to 2014–15.

Summary of key messages:

  • Tonsillectomy rates have remained steady over the last six years at around 4 per 1000 children.
  • Tonsillectomy rates were significantly higher in the non-Māori/non-Pacific ethnic group compared with Māori and Pacific peoples.
  • The level of variation between DHBs remained consistently wide at around three-fold.
  • Ventilation tube (grommet) insertion rates between 2012–13 and 2014–15 were significantly lower than the previous three years.
  • Rates were significantly higher in Pacific peoples than either Māori or non-Māori/non-Pacific ethnic groups.
  • The level of variation between DHBs remained greater than two-fold.

doctor looking through microscope

Tonsillectomy rates have remained steady over the last six years; rates were significantly higher in the non-Māori/non-Pacific group

  • Over a six-year period the average tonsillectomy rate in New Zealand remained fairly steady at around 4.0 per 1000 children.
  • Unlike previous analyses, there was a significant difference between ethnic groups. The non-Māori/non-Pacific group had significantly higher rates than Māori and Pacific peoples. The rates in Pacific peoples were significantly lower than all other ethnic groups.
  • As expected, rates were significantly lower in those aged 10–14 years compared with those aged 5–9.

Ventilation tube (grommets) insertion rates have significantly reduced; rates were significantly higher in Māori and Pacific peoples

  • Rates have significantly reduced from 6.7 per 1000 children in 2009–10 to 5.9 per 1000 children in 2014–15. If private surgical data were included, we could understand whether or not there has been a corresponding increase in private provision.
  • Grommet insertion rates were significantly higher in Māori and Pacific peoples than non-Māori/non-Pacific ethnic groups, at 6.3, 6.6 and 5.7 per 1000, respectively.
  • As expected, rates were significantly higher in the age groups 0–4 and 5–9 years compared with those aged 10–14.

The prevalence of otitis media (middle ear infection) is believed to be higher in Māori and Pacific children, but accurate estimates of national prevalence are not available. Failure rates of tympanometry screening, a test for chronic middle ear disease, can be used as a proxy for otitis media. A 2005–06 report found the highest tympanometry failure rates were in Pacific (11.2 percent) and Māori (10.3 percent) children, with children of European and other ethnicities reporting a failure rate of around 4 percent [1].

There are a number of plausible reasons why grommet insertion rates have reduced. Some factors only apply to one region. It would be interesting to know what may have contributed to a rate drop in other regions. These factors include:

  1. The Haemophilus influenzae vaccine coupled with the 2007 addition of pneumococcal conjugate vaccine to the immunisation schedule and increasing childhood immunisation rates since 2007–08 may have reduced the incidence of otitis media in the community[2].
  2. Free primary health care for under 6-year-olds may be affecting rates or severity of otitis media with effusion (OME).
  3. In one region, additional staffing levels have allowed for a dedicated ear nose and throat specialist assisted by ear nurse specialists to see most children with OME. This consistency allows for better review and monitoring of cases.
  4. In one region, additional audiology services with a full complement of audiologists has brought about better monitoring of children's hearing and better decision-making. Some children whose ears discharge constantly with grommets have received hearing aids instead.
  5. Surgical decision-making may be more conservative than in the past, with the risk–benefit ratio of grommets becoming less favourable due to the risk of adverse effects like eardrum perforation, scarring and retraction.



Tonsillectomy is the removal of one or both tonsils, usually in response to repeat acute tonsillitis or to treat sleep-disordered breathing. Frequently, the adenoids are removed at the same time – adenotonsillectomy.

For the treatment of repeat acute tonsillitis, the criteria for surgery are based on the number of episodes in a 6- or 12-month period. Typically, this is around six or more clinically significant sore-throat episodes in one year, or fewer attacks occurring annually over two or more years. Recent international guidance recommends watchful waiting for those whose sore throats are mild and recommends surgery only be performed when the sore throat is disabling and prevents normal functioning[3].

Sleep-disordered breathing and obstructive sleep apnoea are conditions where upper airway obstruction during sleep results in poor-quality sleep, daytime fatigue, poor school performance and, in severe cases, serious disorders of cardiopulmonary function.

Ventilation tube insertion (grommets)

Otitis media is a common childhood infection, with up to 80 percent of children estimated to have at least one episode by three years of age[4]. Otitis media is most commonly caused by Eustachian tube dysfunction as a result of swollen mucous membranes in the nasopharynx, itself a result of upper respiratory tract infection or allergy.

There are three subtypes of otitis media:

  1. acute otitis media (AOM)
  2. recurrent AOM
  3. OME.

In New Zealand, AOM has been estimated to affect 273 per 1000 children aged 0–4 years each year[5]. Of these, 74 percent of children have one episode, whilst 4 percent may experience recurrent AOM. Recurrent AOM is characterised by repeat acute middle ear infections, typically defined as three to six infections over a six-month period or six or more episodes in a 12-month period.

OME (also known as glue ear) is the presence of fluid (effusion) in the middle ear without an acute infection. OME is common, with a bimodal peak in young children at two and five years of age. By 10 years of age, 80 percent of children will have had at least one episode[4] and most episodes resolve spontaneously.

Children experiencing recurrent AOM or OME may require surgical intervention, which involves the insertion of ventilation tubes (grommets). The decision is usually based on two factors:

  • the number of episodes of AOM experienced over six months or a year, and/or
  • the presence of symptoms such as hearing loss, speech and language delay, and learning problems associated with a middle ear effusion affecting both ears and documented as present for three months or longer.

Systematic reviews report that grommets improves hearing for those with OME and associated hearing loss during the first six months of follow-up but that there is no effect on language development or cognition in otherwise healthy children[6,7]. For children with recurrent AOM, systematic review evidence indicates grommets are effective in preventing/reducing infections in the first six months[8]. Most grommets last for 6–12 months. Available evidence suggests parents perceive improvement in general health, behaviour and social skills in their children following grommet insertion, however, the quality of the studies does not allow strong conclusions to be drawn.

When interpreting the Atlas data, it is important to consider the New Zealand context, as rates of both recurrent AOM and OME are higher in Māori and Pacific peoples populations and these populations are not represented in international studies. This means international guidelines should be interpreted with caution.

Data for these Atlas domains were drawn from the National Minimum Dataset. Data presented are rates of publically funded procedures by district health board (DHB), over a five-year period (2009–14 financial years), by age and ethnicity. If data from private hospitals was included, the procedure rate is likely to change in some regions. Available data was not sufficiently robust to allow analysis of the indications for surgery.

International comparison

The rates reported above are for children aged 0–14 years. Comparable data for the UK and USA uses a 0–17 age band, so the rates reported above have been recalculated using this age group.

Country Variation in ventilation tube insertion rates per 1000, ages 0–17 years

Country Variation in ventilation tube insertion rates per 1000, ages 0–17 years
New Zealand (2007–10) 3.0–7.0
UK (2007–10) 0.62–4.95
USA (2007–10) 3.4–15.2

Questions the data might prompt:

  • Do DHBs have referral and intervention guidelines based on international best practice and agreed between general practitioners and surgeons?
  • For each procedure, what are the most common indications for surgery?
  • How do factors such as resource allocation or the availability of private surgery influence intervention rates?
  • Does the uptake of private health insurance impact on the number of tonsillectomy and ventilation tube insertion operations undertaken in public hospitals? Are rates of private insurance uptake changing?
  • Is the observed variation clinically meaningful?
  • Should intervention rates be higher in Pacific and Māori children?
  • Do DHBs with low grommet insertion rates have higher rates of tympanoplasty and mastoidectomy, reflecting higher rates of untreated middle ear disease?
  • Do high rates for grommet insertion lead to a high later myringoplasty rate, reflecting persistent tympanic membrane perforation after grommet extrusion?

Reading list

Byars SG, Stearns SC, Boomsma JJ. Association of Long-Term Risk of Respiratory, Allergic, and Infectious Diseases With Removal of Adenoids and Tonsils in Childhood. JAMA Otolaryngol Head Neck Surg. Published online 7 June 2018. doi:10.1001/jamaoto.2018.0614. URL: external link (accessed June 2018).



  1. Greville Consulting for National Audiology Centre. 2006. New Zealand Vision and Hearing Screening Report: July 2005 – June 2006. Auckland: Auckland District Health Board.
  2. Walls T, et al. 2011. Vaccination to prevent otitis media in New Zealand. NZMJ 124(1340): 6–9.
  3. Scottish Intercollegiate Guidelines Network. 2010. Management of sore throat and indications for tonsillectomy: A national clinical guideline. Edinburgh: Scottish Intercollegiate Guidelines Network.
  4. Teele DW, Klein JO, Rosner B. 1989. Epidemiology of otitis media during the first seven years of life in children in greater Boston: a prospective, cohort study. J Infect Dis 160(1): 83–94.
  5. Gribben B, et al. 2012. The incidence of acute otitis media in New Zealand children under five years of age in the primary care setting. J Prim Health Care 4(3): 205–12.
  6. National Collaborating Centre for Women’s and Children’s Health. 2008. Surgical management of otitis media with effusion in children. London: RCOG Press.
  7. Browning GG, et al. Grommets (ventilation tubes) for hearing loss associated with otitis media with effusion in children. Cochrane Database Syst Rev 2010, Issue 10, Art. No. CD001801.
  8. McDonald S, Langton Hewer CD, Nunez DA. Grommets (ventilation tubes) for recurrent acute otitis media in children. Cochrane Database Syst Rev 2008, Issue 4, Art. No. CD004741.

Last updated 26/06/2019