Connected Health Cities COPD Algorithm v1.0

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Stata Code can be downloaded from GitHub repository

Development and validation of diagnostic coding algorithm Acute exacerbation of COPD is one of the most common reasons for emergency admission to hospital. The standard approach for identifying admissions within administrative data is to focus exclusively on the primary (principal) discharge diagnosis code. However, extending the analysis to the secondary codes gives a more realistic picture of the number of admissions.

Hospital data for each admission are always recorded, and the information includes not only the individual’s demographics, but also details of their progress through the system and, importantly, the clinical diagnosis. The diagnosis is recorded with a series of ICD10 codes (international coding descriptors - https://icd.who.int/browse10/2016/en) that are entered by coders working from the clinical record after discharge. Clinical records are not didactic, and often diagnoses develop over the course of an admission – and indeed may remain as probable, rather than certain, because of the biological variability with which conditions manifest.

Our algorithm is designed as follows:

• Restricting to emergency admissions The Secondary Uses Service (SUS) data separate hospital admissions according to whether they are:
• emergencies (referred as emergency from clinics, another hospital, GP or the ED); or
• elective, i.e. a planned admission for specific investigation or procedure

COPD exacerbations present as unexpected emergencies so the first filter is to restrict the analysis to emergency. The relevant codes for emergency admissions are:

21
22
23
24
25
2A
2B
2C
2D
28
“”

1. Restricting to emergencies admitted to “medical wards”

Each hospital bed is coded with a specialty. When COPD is the primary reason for the admission, hospital processes direct that admission towards a medical bed (i.e. under the care of a physician), rather than any other bed (e.g. surgical, psychiatric, orthopaedic, obstetric etc.). Thus, it is rational to presume that an admission that includes a COPD code to any other speciality is using the COPD code to describe a co-morbid condition. The list of relevant medical speciality codes are included in appendix 1.

’

1. Restricting to final episode of spell

The coding system is set out in units of Finished Consultant Episodes, or FCEs. These are defined such that when a patient”moves from the care of”one consultant to the care of a second, each different consultant’s input can be evaluated. Importantly, for our purposes, it is only at the end of a spell, i.e. end of the final episode, when the fullest diagnosis will have been apparent, and that is therefore the episode we use to define the diagnosis of the spell. ‘’

1. Identifying those admissions which are likely to be related to COPD””

We have 3 lists of ICD10 codes used when running our algorithm. These are shown in appendix 2.

• e Stata .do file associated with this document does not include code for steps 1 to 3 above as the variable names associated with the filters can change between datasets. The Stata .do file is concerned with step 4. It creates variables as outlined below:
• e first step is to assign a new variable called ‘status1’. The value for status1 is calculated for each episode as follows:
• if any of list 1 are in the primary diagnosis field, then status1 = 1
• if any of list 2 are in the primary diagnosis field, then status1 = 2
• if any of list 3 are in the primary diagnosis field, then status1 = 3
• if none of the above conditions are met then status1 = 0
• The next step is to assign a new variable called ‘status2’. The value for status2 is calculated for each episode as follows: ‘’’’’’’’’’’’
• if any of list 1 are in the first secondary diagnosis field, then status2 = 1
• if any of list 2 are ‘n the f’rst secondary diagnosis field, then status2 = 2’’’’
• if any of list 3 are in the first secondary diagnosis field, then status2 = 3
• if none of the above conditions are met then status2 = 0

The next step is to assign a new variable called ‘status3’. The value for status3 is calculated for each episode as follows:

• if any of list 1 are in the second secondary diagnosis field, then status3 = 1
• if any of list 2 are in the second secondary diagnosis field, then status3 = 2
• if any of list 3 are in the second secondary diagnosis field, then status3 = 3
• if none of the above conditions are met then status3 = 0

We then add a variable entitled ‘statusoutcome’. The value for statusoutcome is based upon the values of status1, status 2 and status 3; and is calculated for each episode as follows

• if status1 = 2 & status2 = 2 & status3 = 1, then statusoutcome = 7
• if status1 = 3 & status2 = 3 & status3 = 1, then statusoutcome = 6
• if status1 = 2 & status2 = 3 & status3 = 1, then statusoutcome = 5
• if status1 = 3 & status2 = 2 & status3 = 1, then statusoutcome = 4
• if status1 = 3 & status2 = 1, then statusoutcome = 3
• if status1 = 2 & status2 = 1, then statusoutcome = 2
• if status1 = 1, then statusoutcome = 1
• if none of the above conditions are met then status3 = 0

We then add a variable entitled ‘copdcategory’. The value for copdcategory is calculated for each episode as follows:

• if statusoutcome = 1 then copdcategory = 1
• if statusoutcome = 2 OR statusoutcome = 4 OR statusoutcome = 5 OR statusoutcome = 7 then copdcategory = 2
• if statusoutcome = 3 OR statusoutcome = 6 then copdcategory = 3
• if none of the above conditions are met then copdcategory = 0

We then add a variable entitled ‘copdcat1’. The value for copdcat1 is calculated for each episode as follows:

• if copdcategory > 0 then copdcat1 = 1
• if copdcategory = 0 then copdcat1 = 0

The admissions where copdcat1 are equal to 1 are, therefore, our defined cohort of COPD admissions.

APPENDIX 1: MEDICAL SPECIALTY CODES

The seizures algorithm requires that the treatment speciality is one of the following codes:

180 Accident and Emergency
192 Critical Care Medicine
300 General Medicine
301 Gastroenterology
302 Endocrinology
303 Clinical Haematology
305 Clinical Pharmacology
314 Rehabilitation
315 Palliative Medicine
320 Cardiology
330 Dermatology
340 Respiratory Medicine
350 Infectious Diseases
361 Nephrology
370 Medical Oncology
400 Neurology
410 Rheumatology
430 Geriatric Medicine
820 General Pathology
823 Haematology
960 Allied Health Professional Episode
 

APPENDIX 2: ICD10 CODES WHICH DENOTE A PROBABLE COPD ADMISSION

List 1:

J40X Bronchitis not specified as acute or chronic
J410 Simple chronic bronchitis
J411 Mucopurulent chronic bronchitis
J418 Mixed simple and mucopurulent chronic bronchitis
J42X Unspecified chronic bronchitis
J430 MacLeod s syndrome
J431 Panlobular emphysema
J432 Centrilobular emphysema
J438 Other emphysema
J439 Emphysema unspecified
J440 Chronic obstruct pulmonary dis with acute lower resp infec
J441 Chron obstruct pulmonary dis wth acute exacerbation unspec
J448 Other specified chronic obstructive pulmonary disease
J449 Chronic obstructive pulmonary disease unspecified

List 2: B59X Pneumocystosis
J100 Influenza with pneumonia influenza virus identified
J101 Influenza with oth resp manifest influenza virus identified
J108 Influenza with other manifest influenza virus identified
J110 Influenza with pneumonia virus not identified
J111 Influenza with oth resp manifestation virus not identified
J118 Influenza with other manifestations virus not identified
J120 Adenoviral pneumonia
J121 Respiratory syncytial virus pneumonia
J122 Parainfluenza virus pneumonia
J128 Other viral pneumonia
J129 Viral pneumonia unspecified
J13X Pneumonia due to Streptococcus pneumoniae
J14X Pneumonia due to Haemophilus influenzae
J150 Pneumonia due to Klebsiella pneumoniae
J151 Pneumonia due to Pseudomonas
J152 Pneumonia due to staphylococcus
J153 Pneumonia due to streptococcus group B
J154 Pneumonia due to other streptococci
J155 Pneumonia due to Escherichia coli
J156 Pneumonia due to other aerobic Gram-negative bacteria
J157 Pneumonia due to Mycoplasma pneumoniae
J158 Other bacterial pneumonia
J159 Bacterial pneumonia unspecified
J160 Chlamydial pneumonia
J168 Pneumonia due to other specified infectious organisms
J170 Pneumonia in bacterial diseases classified elsewhere
J171 Pneumonia in viral diseases classified elsewhere
J172 Pneumonia in mycoses
J173 Pneumonia in parasitic diseases
J178 Pneumonia in other diseases classified elsewhere
J180 Bronchopneumonia unspecified
J181 Lobar pneumonia unspecified
J182 Hypostatic pneumonia unspecified
J188 Other pneumonia organism unspecified
J189 Pneumonia unspecified
J200 Acute bronchitis due to Mycoplasma pneumoniae
J201 Acute bronchitis due to Haemophilus influenzae
J202 Acute bronchitis due to streptococcus
J203 Acute bronchitis due to coxsackievirus
J204 Acute bronchitis due to parainfluenza virus
J205 Acute bronchitis due to respiratory syncytial virus
J206 Acute bronchitis due to rhinovirus
J207 Acute bronchitis due to echovirus
J208 Acute bronchitis due to other specified organisms
J209 Acute bronchitis unspecified
J210 Acute bronchiolitis due to respiratory syncytial virus
J218 Acute bronchiolitis due to other specified organisms
J219 Acute bronchiolitis unspecified
J22X Unspecified acute lower respiratory infection
J690 Pneumonitis due to food and vomit
J851 Abscess of lung with pneumonia
J852 Abscess of lung without pneumonia
J860 Pyothorax with fistula
J869 Pyothorax without fistula

List 3: R042 Haemoptysis
R048 Haemorrhage from other sites in respiratory passages
R05X Cough
R060 Dyspnoea
R062 Wheezing
R064 Hyperventilation
R066 Hiccough
R068 Other and unspecified abnormalities of breathing
R070 Pain in throat
R071 Chest pain on breathing
R072 Precordial pain
R073 Other chest pain
R074 Chest pain unspecified
R091 Pleurisy
R092 Respiratory arrest
R093 Abnormal sputum
R098 Oth spec symptoms and signs involving circ and resp systems
R202 Paraesthesia of skin
R208 Other and unspecified disturbances of skin sensation
R232 Flushing
R233 Spontaneous ecchymoses
R400 Somnolence
R401 Stupor
R402 Coma unspecified
R460 Very low level of personal hygiene
R500 Fever with chills
R509 Fever unspecified
R51X Headache
R600 Localized oedema
R601 Generalized oedema
R609 Oedema unspecified

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