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Ambulatory Care Sensitive Conditions (ACSC)

Analysis of certain conditions for which unplanned hospitalisation may be prevented or reduced by provision of care in primary or community settings. This analysis generates insight about the characteristics of the ACSC admissions, their length of stay and the related readmissions.

Ambulatory care sensitive conditions (ACSC) are conditions where hospital admissions may be prevented by interventions in primary care. (Purdy et al, 2009)

Effective treatment of acute conditions, good management of chronic illnesses, and immunisation against infectious diseases can reduce the risk of a specified set of hospitalisations. (Sundmacher et al, 2015)

The most frequently used subset of ACSC in the NHS contains 19 conditions. These are classified as:

  • chronic - effective management prevents flare-ups
  • acute - early intervention may prevent more serious progression
  • vaccine-preventable - where immunisation and other interventions minimise the onset of certain illnesses (Ham et al, 2010)

Appendix A lists the International Classification of Diseases (ICD) 10 codes used to identify each condition. Seven conditions account for three-quarters of all ACSCs spells:

  • influenza and pneumonia
  • chronic obstructive pulmonary disease (COPD)
  • ear, nose and throat infections
  • convulsions and epilepsy
  • diabetes complications
  • cellulitis
  • asthma

The unit of analysis for ACSC in this report is a continuous inpatient (CIP) spell. A CIP spell is a continuous period of care in hospital including any transfers between hospitals which might take place during the period. It can include more than one episode or healthcare provider. An episode is a continuous period of admitted patient care under one consultant by one healthcare provider. 

An ACSC spell or ACSC admission refers to a CIP spell where the first episode in the spell has an ACSC condition. In this analysis, only one ACSC condition is assigned per spell. All ACSC spells are subsets of emergency or unplanned spells; they represent 5% of all Admitted Patient Care (APC) spells and nearly 15% of emergency spells. High levels of admissions for ACSC may imply poor coordination between primary and secondary care, (NHS England, 2014), and may be a sign of the poor overall quality of care received in the community. Around 76% of all ACSC spells have Accident and Emergency department as the admission method, whereas 15.5% are GP referrals.

In general, ACSCs spells display strong seasonality; the highest levels usually occur in January and the lowest in August. Spells have increased at a higher rate than the overall inpatient (APC) activity in the last five years.

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Ambulatory care sensitive conditions spells and length of stay

More than half of all ACSC spells (53.6%) fall into the chronic classification. However, influenza and pneumonia, within the vaccine preventable classification, has the highest number of cases. Listed are the four conditions which show the highest number of spells; these account for 52% of all ACSC spells:

  • influenza and pneumonia 
  • COPD 
  • ear, nose and throat infections 
  • convulsions and epilepsy 

The length of stay (LoS) is the duration of a spell, that is, the number of days between admission and discharge. The mean LoS has decreased by one day in the last four years. Almost a quarter (24%) of ACSC spells have a duration (LoS) of zero days, 99% have a LoS less than or equal to 50 days, and 96.8% have a LoS less than or equal to 30 days.

The LoS by ACSC condition presents huge variability ranging from a mean of 0.72 to 24.7 days. For example, nutritional deficiencies present the highest LoS with a mean of 24.7 days; however, this is a rare condition (0.0074% of all ACSC spells). Conversely, influenza and pneumonia has an average LoS close to 11 days and is at the top of the list for a number of spells accounting for 16% of them. Improvements in the prevention of these conditions would potentially lead to benefits (for example, a reduction in demand on front line services or improved health and well being) if health providers focus on preventing the occurrence of this condition.

Children under 5 and the elderly have the largest volume of ACSC spells when standardised by age. There is a broadly linear relationship between age and average LoS, with under 5s staying one day and patients aged 90 and over staying for 11 days.

Use the button on the top right-hand side to filter for patients who have had a readmission (readmitted within 29 days). By doing this, it can be observed that COPD becomes the condition with more spells, that is 19% of all the ACSC re-admissions. It also shows that the mean LoS for patients who had a readmission is around a day longer.

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Zero length of stay

The proportion of ACSC spells to all APC spells has increased from 4.4% in 2013 to 4.9% in 2017, and to 5.1 in 2018. Likewise, ACSC spells with a LoS of zero days have risen from 0.9% in 2013 to 1.3% in 2018.

ACSC spells with LoS of more than zero days have also increased from 3.5% to 3.8% during the same period. ACSC spells with a LoS of zero days account for 23.4% of the ACSC spells. However, this proportion changes considerably when looking at individual conditions. 

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The greatest increase in spells with respect to 2014 has been observed for hypertension (80% increase), followed by iron deficiency (anaemia) with 53% increase, influenza and pneumonia 47% increase, and diabetes complications with a 39% increase.

There are few conditions which have decreased with respect to 2014:

  • asthma
  • convulsions and epilepsy
  • angina 
  • perforated bleeding ulcer

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Deprivation and ethnicity

Higher ACSC admission rates are associated with lower incomes in a number of studies in other countries, and this appears to be similar for England. It has been observed that the highest number of ACSC spells is for the 10% most deprived areas, whilst the 10% least deprived areas have the lowest number of ACSC spells. With respect to LoS, the trend is almost inversely proportional with a difference of one day on average LoS between the most and least deprived.

Ethnicity appears to be strongly associated with LoS. For each ethnic group, LoS shows little variation across the years. White Irish, Caribbean and White British present the greatest LoS with 6.2, 5.5 and 5.3, respectively. This could be explained by the incidence of some conditions - which are higher for some ethnicities. For example, while ear, nose and throat infections is the most common condition for the other ethnicities (with 24% of their spells accounting for it), this is not the case for White Irish, Caribbean and White British who have 4.8%, 7.9% and 10.9%, respectively. This condition accounts for a LoS of less than one day. The most common condition for Caribbean is diabetes complication (20.2%) which represents a mean LoS of 8.8 days. For White British and White Irish, the most common conditions are COPD (mean LoS of 5.4 days), and influenza and pneumonia (mean LoS of 10.9 days).

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The following report gives an overview of the conditions affecting specific ages. Ear, nose and throat infections, asthma, convulsions and epilepsy, and influenza and pneumonia, are the main conditions which affect children under the age of five. COPD, influenza and pneumonia, congestive heart failure and angina, are the main conditions affecting people over 65.

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Readmissions and length of stay

For the purposes of this report, readmission is defined as when a patient has been admitted to hospital within 29 days from the previous discharge. If the previous admission also counted as an ACSC spell, then this admission is an ACSC readmission. Nearly 18% of all ACSC spells have a readmission.

Patients who were readmitted stayed, on average, one day more than those who were not readmitted (6.9 vs. 5.8 days), and 17.8% of ACSC spells have had a readmission. COPD admissions accounted for 19.2% of all ACSC readmissions and 41% of ACSC readmissions have happened within a week.

82% of the spells of patients who are readmitted came back within 20 days of being discharged.

For readmitted patients, younger patients tend to be readmitted in a shorter time than older patients.

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Demographics of readmissions

The 10% most deprived areas account for the highest proportion of readmissions; by contrast, the least deprived 10% areas have the lowest proportion. White Irish, White British and Caribbean, with the longest mean LoS, have also the highest rates for readmissions with 22%, 19%, and 19%, respectively.

Hospital admissions for ambulatory care sensitive conditions (ACSCs) may be prevented by effective ambulatory management and treatment. ACSC admissions are used as an indicator for primary care quality and accessibility; however, the debate around to which extent these admissions are truly preventable continues. (Marieke et al 2019) Various studies have also shown that non-ambulatory care factors (for example hospital bed availability, coordination of care, per capita income in the region, geographical features and social disadvantage) influence ACSC admissions (Muenchberger, Kendall 2010).

What can be done to reduce the preventable ACSC admissions? A study (Tobias et al, 2013) from the perspective of primary care physicians suggests creating strategies to target after-hours care, optimal use of ambulatory services, intensified monitoring of high-risk patients, initiatives to improve patients’ willingness and ability to seek timely help, and patient’s medication adherence. A systematic review of 1778 publications concluded that the evidence for chronic ACSC admissions suggests that strong primary care in terms of adequate primary care physician supply and long-term relationships between primary care physicians and patients reduces hospitalisations for chronic ACSCs. However, there is a lack of evidence for the positive effects of many other organisational primary care aspects, such as specific disease management programs (van Loenen et al, 2014).

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Ansari Z. (2007) The Concept and Usefulness of Ambulatory Care Sensitive Conditions as Indicators of Quality and Access to Primary Health Care. Australian Journal of Primary Health 13, 91-110.

Freund T,  Campbell S M,  Geissler S,  Kunz C U,  Mahler C,  Peters-Klimm F ,  Szecsenyi J. (2013).  Strategies for Reducing Potentially Avoidable Hospitalizations for Ambulatory Care–Sensitive Conditions. Ann Fam Med 11 (4): 363-370. doi: 10.1370/afm.1498

Ham C, Imison C, Jennings M. (2010). Avoiding Hospital Admissions: Lessons from evidence and experience. London: The King’s Fund.  (accessed on 20 February 2019)

Muenchberger H, KendallE. (2010) Predictors of preventable hospitalization in chronic disease: priorities for change. J Public Health Policy; 31:150–63.

NHS England (2014) Emergency Admissions for Ambulatory Care Sensitive Conditions -characteristics and trends at national level. (2014). NHS England (3).

Paul MC, Dik JH, Hoekstra T, van Dijk CE. (2018) Admissions for ambulatory care sensitive conditions: a national observational study in the general and COPD population, European Journal of Public Health, Volume 29, Issue 2, April 2019, Pages 213–219,

Purdy S, Griffin T, Salisbury C. (2009) Ambulatory care sensitive conditions: terminology and disease coding need to be more specific to aid policy makers and clinicians. Public Health; 123:169–73. DOI:10.1016/j.puhe.2008.11.001

Sundmacher, L., Fischbach, D., Schuettig, W., Naumann, C., Augustin, U., & Faisst, C. (2015). Which hospitalisations are ambulatory care-sensitive, to what degree, and how could the rates be reduced? Results of a group consensus study in Germany. Health Policy, 119(11), 1415–1423.

Van Loenen T, Van den Berg M J, Westert G P, Faber M J (2014). Organizational aspects of primary care related to avoidable hospitalization: a systematic review, Family Practice, Volume 31, Issue 5, October 2014, Pages 502–516,

Last edited: 28 September 2020 12:13 pm