# I02040 Emergency readmissions within 30 days of discharge from hospital - specification v3

This indicator measures the percentage of emergency admissions to any hospital in England occurring within 30 days of the most recent discharge from hospital.

Admissions for cancer and obstetrics are excluded as they may be part of the patient’s care plan.

Results are presented as trends across a range of geographies, age bands and by sex.

This indicator forms part of the Hospital Care Domain.

Page contents

## Indicator details

### Technical description

Indirectly age, sex, method of admission and diagnosis/procedure standardised percentage of emergency admissions to any hospital (includes activity in English NHS Hospitals and English NHS commissioned activity in the independent sector) in England occurring within 30 days of the last, previous discharge from hospital after admission.

Admissions for cancer and obstetrics are excluded.

Results are presented as trends fixed on the first year of the series and further broken down by Geographies (Local Authority of Residence, Region, ONS Area Classification, NHS and Private Providers, NHS England Region, Sustainability and Transformation Partnerships (STP) and Clinical Commissioning Groups (CCG)), Deprivation (Index of Multiple Deprivation (IMD 2019) Quintiles), Age bands (<16 years, 16+ years, 16-74 years; 75+ years) and sex (Male, Female and Persons).

(Note: when using indirect standardisation, it is inappropriate to compare sub-geographies with each other – all comparisons should be made with the national figure.)

#### Denominator

The number of finished CIP spells within selected medical and surgical specialties with a discharge date up to 31st March in the financial year of analysis.

The denominator is further filtered by the age and sex for each of the breakdown combinations below:

• 16+ years and female only, and male only and both male and female (persons)
• 16-74 years and female only, and male only and both male and female (persons)
• 75+ years and female only, and male only and both male and female (persons)
• <16 years and female only, and male only and both male and female (persons)

#### Numerator

The number of finished and unfinished CIP spells intersecting the respective financial year, plus those up to 30 days into the next financial year that are emergency admissions within 0-29 days (inclusive) of the last, previous discharge from hospital.

I02040

#### Disclosure control

The indicator is calculated following HES guidance on suppression of small numbers.

## Data Sources

The records for the denominator and the numerator are taken from Hospital Episode Statistics for Admitted Patient Care (HES APC) linked as Continuous Inpatient (CIP) Spells.

http://webarchive.nationalarchives.gov.uk/20180328130852tf_/http://content.digital.nhs.uk/media/11859/Provider-Spells-Methodology/pdf/Spells_Methodology.pdf

## Construction

This section sets out how this indicator is constructed.

### Denominator

The number of finished CIP spells with a valid Geographic value[2], within selected medical and surgical specialties, with a discharge date up to 31st March within the financial year of analysis. Day cases, spells with a discharge coded as death, maternity spells (based on specialty, admission or discharge episode type and primary diagnosis), and those with mention of a diagnosis of cancer or chemotherapy for cancer anywhere in the spell are excluded. Patients with mention of a diagnosis of cancer or chemotherapy for cancer anywhere in the 365 days prior to admission are also excluded.

[2] The indicator calculates across a range of geographies (Lower tier local authority, Region, ONS Area Classification, Provider, CCG, STP and NHS England Region) the value must be valid to be included for the geography being reported. Deprivation is the exception as instances where no valid value is included.

The following fields and values are used to filter the denominator.

#### The CIP Spell has:

DISDATE (discharge date)

Filters the whole period of the financial year being reported on., e.g. between 01/04/2017 and 31/03/2018 inclusive AND is equal to or after the ADMIDATE (date of admission).

DISMETH (method of discharge)

1 or 3 (Discharged on clinical advice or discharged by a mental health review tribunal, i.e. not died, self-discharged or a baby or still in hospital).

Contains: 11, 12, 13, 21, 22, 23, 24, 25, 28, 2A, 2B, 2C, 2D, 31, 32, 81, 82, 83, 84 or 89.

#### The FIRST episode in the CIP spell has:

EPIORDER (episode order)

Equals 1.

Geography (field dependent on the Geography being processed)

Valid value i.e. a known Geography code for the reporting year, i.e. excludes unknowns.  Note: legacy geographies are mapped to new organisation codes when known.  There is an exception for IMD where all invalid values are grouped for reporting.

EPITYPE (episode type)

Equals 1.  General episode types only.

CLASSPAT (patient classification)

STARTAGE (age at start of episode)

Value between 0 and 120 and 7001 and 7007 only.  Value between 7001 and 7007 are converted to 0.  Note: values are used later to filter into the reporting Age bands: <16 years, 16+ years, 16-74 years; 75+ years.

DOB (patient date of birth)

Not 01/01/1900 or 01/01/1901 representing unknown.

SEX (sex of patient)

Equals 1 (male) or 2 (female).  Note: values are used later to filter into the reporting groups: male only, female only and persons (male and female).

#### AND the LAST episode in the CIP spell has:

EPITYPE (episode type)

Equals 1.  General episode types only.

#### AND exclude the whole CIP spell where ANY episode in the spell has:

DIAG_01 - DIAG_20 (any diagnosis)

C00*-C97*, D37*-D48* (any mention of a diagnosis of cancer) OR Z51.1* (any mention of chemotherapy for cancer).  Applies both within the reporting year or anywhere in the 365 days prior to admission for the patient.

#### OR

TRETSPEF (the specialised service within which the Patient is treated)

Not 501, 560, 610.

DIAG_01 (primary diagnosis)

Does not begin with ‘O’ (Obstetrics).

There is an additional 3 step piece of logic which is designed to ensure that the spells are allocated to the most appropriate diagnosis/procedure group for standardisation:

#### Step A

Searching all episodes from first to last, identify spells where there is a valid procedure (i.e. not being either: (1) a null value, (2) "-" meaning “no operation performed”, (3) "&" meaning “not known”.) and surgical specialty (taken from the episode where the procedure was found).  These spells are standardised by procedure subgroup (procedures beginning with ‘Y’ or ‘Z’ are standardised in the ‘no procedure’ basket).

#### Step B

Excluding spells selected in step A, select spells where treatment function specialty in the first episode is surgical, these spells are standardised under the ‘no procedures’ basket.

#### Step C

Excluding those spells selected in step A and step B, select spells where treatment function specialty of the first episode is medical.  These spells are standardised by diagnosis subgroup.

In all cases the first three characters of the respective diagnosis or procedure code is used.

Lists of specialties and sub-groups used above for filtering/standardisation are:

Medical Specialties: 190, 192, 223, 242, 251, 252, 253, 254, 255, 256, 257, 258, 259, 260, 261, 262, 263, 264, 300, 301, 302, 303, 304, 305, 306, 307, 308, 309, 310, 311, 313, 314, 315, 316, 317, 318, 319, 320, 321, 322, 323, 324, 325, 327, 328, 329, 330, 331, 340, 341, 342, 343, 344, 345, 346, 350, 352, 360, 361, 370, 371, 400, 401, 410, 420, 421, 422, 424, 430, 450, 460, 501, 502, 503, 510, 520, 560, 610, 620.

Surgical Specialties: 100, 101, 102, 103, 104, 105, 106, 107, 108, 110, 120, 130, 140, 141, 142, 143, 144, 150, 160, 161, 170, 171, 172, 173, 174, 180, 191, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 241.

### Numerator

The number of finished and unfinished CIP spells that are emergency admissions within 0-29 days (inclusive) of the last, previous discharge from hospital (see denominator), including those where the patient dies, but excluding the following: those with a treatment function and primary diagnosis upon readmission coded under obstetrics and those where the readmitting spell has a diagnosis of cancer (other than benign or in situ) or chemotherapy for cancer coded anywhere in the spell.

The date of the last, previous discharge from hospital, and the date and method of admission from the following CIP spell, are used to determine the interval between discharge and emergency readmission.

The numerator is based on a pair of spells, the discharge spell and the next subsequent readmission spell (this spell must meet the numerator criteria).  The selection process thus carries over the characteristics of the denominator for the discharge spell and applies additional ones to the readmission spell.

The following fields and values are used for the numerator:

#### The CIP spell has:

Between 1st April of the financial year reporting on and 30th April of the following year.  Filters the whole period of the financial year being reported on plus one month., e.g. between 01/04/2017 and 30/04/2018 inclusive.

Contains: 21, 22, 23, 24, 25, 28, 2A, 2B, 2C, or 2D (emergency admissions).

#### The FIRST episode in the CIP spell has:

EPIORDER (episode order)

Equals 1.

Geography (field dependent on the Geography being processed)

Valid value i.e. a known Geography code for the reporting year, i.e. excludes unknowns.  Note: legacy geographies are mapped to new organisation codes when known.  There is an exception for IMD where all invalid values are grouped for reporting.

EPITYPE (episode type)

Equals 1.  General episode types only.

CLASSPAT (patient classification)

AND ADMIDATE from the FIRST episode of the Readmission CIP spell minus DISDATE from the LAST episode in Discharge CIP spell ≤ 29 days.  Note: where there is more than one readmission within 30 days, each readmission is counted once, in relation to the previous discharge.

#### AND exclude where ANY episode in the CIP spell has:

DIAG_01 - DIAG_20 (any diagnosis)

C00*-C97*, D37*-D48* (any mention of a diagnosis of cancer) OR Z51.1* (any mention of chemotherapy for cancer).  Applies both within the reporting year or anywhere in the 365 days prior to admission for the patient.

OR

TRETSPEF (the specialised service within which the patient is treated)

Not 501, 560, 610.

DIAG_01 (primary diagnosis)

Does not begin with ‘O’ (Obstetrics).

## Indirect standardisation

The first step is to calculate the casemix-specific rates for the standard or reference population.  The trends produced can be based on either annual or three-year pooled datasets and the standard population is derived from the mid-point of the series, for example, for a five-year annual trend from 2013/14 to 2017/18 the mid-point year 2015/16 is used as the standard population.  For a three-year pooled trend 2013/16 to 2015/18 the mid-point pool 2014/17 is used as the standard population.

The dataset described above is aggregated with counts of readmissions (numerator) and previous discharges (denominator) grouped by:

• Age based on STARTAGE using the following age bands: <1, 1-4, 5-9, 10-15,16-64, 65-74, 75-84, 85+.  As the indicator is broken down into broader Age bands for reporting the bands used depends on the breakdown:
• <16 years uses: <1, 1-4, 5-9, 10-15
• 16+ years uses: 16-64, 65-74, 75-84, 85+
• 16-74 years uses: 16-64, 65-74
• 75+ years uses: 75-84, 85+
• Sex based on SEX as 1, 2 (male and female). As the indicator is broken down by sex this grouping is only used for the persons reporting category.
• Method of admission of discharge spell based on ADMIMETH as elective or non-elective
• Medical or Surgical specialties based on TRETSPEF.

Then either:

• Diagnosis group (within medical specialties) based on DIAG_01 (primary diagnosis) and expressed to 3 characters

OR

• Procedure group (within surgical specialties) based on OPERTN_01 (primary procedure) expressed to 3 characters.

For each group in this casemix the casemix specific readmission rates are calculated and are then applied to the casemix structure of the subject population e.g. each local authority.  This gives an expected number of events against which the observed number of events may be compared.

Indirect standardisation involves the calculation of the ratio of observed number of events (for the geographic breakdown) and the number of events that would be expected if it had experienced the same event rates as those of patients in England in the standard population and across the mid-point time period, given the casemix of age, sex, method of admission and diagnosis / procedure of its patients..

$${ IS_{Ratio} = \frac {O}{E} \times 100 = \frac {\sum_i O_i}{\sum_i E_i} \times 100 = \frac {\sum_i O_i}{\sum_i n_i \lambda_i} \times 100 }$$

(expressed per 100 denominator population)

where:

$$\mathsf{O_i}$$ is the observed number of events in the subject population in casemix group $$\mathsf{i}$$

$$\mathsf{E_i}$$ is the expected number of events in the subject population in casemix group $$\mathsf{i}$$

$$\mathsf{n_i}$$ is the number of individuals in the subject population in casemix group $$\mathsf{i}$$

$$\mathsf{\lambda_i}$$ is the crude age-specific rate in the standard population in casemix group $$\mathsf{i}$$.

This standardised ratio is then converted into a rate by multiplying it by the overall event rate of patients in England.

$${ IS_{Rate} = \frac {O}{E} \times \lambda \times 100 = \frac {\sum_i O_i}{\sum_i E_i} \times \lambda \times 100 = \frac {\sum_i O_i}{\sum_i n_i \lambda_i} \times \lambda \times 100 }$$

(expressed per 100 denominator population)

where:

$$\mathsf{O_i}$$ is the observed number of events in the subject population in casemix group $$\mathsf{i}$$

$$\mathsf{E_i}$$ is the expected number of events in the subject population in casemix group $$\mathsf{i}$$

$$\mathsf{n_i}$$ is the number of individuals in the subject population in casemix group $$\mathsf{i}$$

$$\mathsf{\lambda_i}$$ is the crude age-specific rate in the standard population in casemix group $$\mathsf{i}$$

$$\mathsf{\lambda}$$ is the overall crude rate in the standard population.

## Confidence intervals

The lower and upper limits of the 95% and 99.8% confidence interval for the indirectly standardised rate are calculated by finding the lower and upper limits of the standardised ratio and multiplying by the overall crude rate of the standard population.  The Byar’s approximation is used as it is a sufficiently accurate approximation to the Poisson probabilities (from Breslow NE and Day NE. Statistical Methods in Cancer Research, Volume II: The Design and Analysis of Cohort Studies. Lyon: International Agency for Research on Cancer, World Health Organization, 1987: 69).

The 95% limits are given by:

$${ IS_{Rate(LL 95.0)} = \frac {O}{E} \times \Bigg \{ 1 - \frac {1}{9O} - \frac {1.96}{\sqrt[3]{(O+1)}} \Bigg \}^3 \times \lambda \times 100 }$$

$${ IS_{Rate(UL 95.0)} = \frac {(O+1)}{E} \times \Bigg \{ 1 - \frac {1}{9(O+1)} + \frac {1.96}{\sqrt[3]{(O+1)}} \Bigg \}^3 \times \lambda \times 100 }$$

The 99.8% limits are given by:

$${ IS_{Rate(LL 99.8)} = \frac {O}{E} \times \Bigg \{ 1 - \frac {1}{9O} - \frac {3.09}{\sqrt[3]{(O+1)}} \Bigg \}^3 \times \lambda \times 100 }$$

$${ IS_{Rate(UL 99.8)} = \frac {(O+1)}{E} \times \Bigg \{ 1 - \frac {1}{9(O+1)} + \frac {3.09}{\sqrt[3]{(O+1)}} \Bigg \}^3 \times \lambda \times 100 }$$

(expressed per 100 denominator population)

where:

$$\mathsf{O}$$ is the total observed number of events in the subject population

$$\mathsf{E}$$ is the total expected number of events in the subject population

$$\mathsf{\lambda}$$ is the overall crude rate in the standard population.

## Excel output

When output to Excel the following data columns are produced:

Column name Output

Year

Financial year being reported.

Period of coverage

Start and end dates of the reporting period.

Breakdown

National, Deprivation quintile, Lower tier local authority, Region, ONS Area Classification, Provider, CCG, STP or NHS England Region.

Level

ONS or ODS codes within each Breakdown.

Level description

Description matching the ONS or ODS codes.

Indicator value

Indirectly standardised percentage rate (ISR).

Lower CI (95%)

ISR lower 95% confidence interval.

Upper CI (95%)

ISR upper 95% confidence interval.

Lower CI (99.8%)

ISR lower 99.8% confidence interval.

Upper CI (99.8%)

ISR upper 99.8% confidence interval.

Numerator

The number of readmissions within 30 days.

Denominator

The number of discharges to end of financial year.

Expected

The expected number of readmissions within 30 days.

Banding

National Comparison, based on 95% and 99.8% confidence intervals of the rate[3].

Warnings

Caution in interpretation of data.  Numbers of patients discharged too small for meaningful comparisons (i.e. below 200).

[3] B1 = Significantly lower than the national average at the 99.8% level; B5 = Significantly lower than the national average at the 95% level but not at the 99.8% level; W = National average lies within expected variation (95% confidence interval); A5 = Significantly higher than the national average at the 95% level but not at the 99.8% level; A1 = Significantly higher than the national average at the 99.8% level.

## CSV output

When output to csv the following data columns are produced:

Column name

Output

Indicator name

Descriptive name for the indicator.

Year

Financial year.

Period of coverage

Start and end dates of the reporting period.

Breakdown

National, Deprivation quintile, Lower tier local authority, Region, ONS Area Classification, Provider, CCG, STP or NHS England Region.

Level

ONS or ODS codes within each Breakdown.

Level description

Description matching the ONS or ODS codes.

Age breakdown

The age band breakdown (if available) or “All” otherwise.

Sex breakdown

The sex breakdown: male, female or persons.

DiagOper breakdown

The diagnosis or procedure breakdown (if applicable) or “All” otherwise.

Trend

Annual or Three-year Pooled Trend.

Indicator value

Indirectly standardised percentage rate (ISR).

Lower CI (95%)

ISR lower 95% confidence interval.

Upper CI (95%)

ISR upper 95% confidence interval.

Lower CI (99.8%)

ISR lower 99.8% confidence interval.

Upper CI (99.8%)

ISR upper 99.8% confidence interval.

Numerator

The number of readmissions within 30 days.

Denominator

The number of discharges to end of financial year.

Expected

The expected number of readmissions within 30 days.

Banding

National Comparison, based on 95% and 99.8% confidence intervals of the rate.

Warnings

Caution in interpretation of data.  Numbers of patients discharged too small for meaningful comparisons (i.e. below 200).

## Revision history

Version

Date

Summary of Changes

1.3

March 2019

Draft based on CCGOIS Readmissions Indicator

2.0

May 2019

First published on NHS Digital Website
3.0 December 2019 Version uplift following changes agreed with the Indicator Consultation Group.

Last edited: 3 August 2020 1:10 pm