Colorectal cancer – standardised 30-day in-hospital mortality ratio following surgery

Metric

The ratio of the observed number of deaths to the expected number of deaths, multiplied by 100.

Numerator

All spells with method of discharge as death (DISMETH=4 or 5), within 30 days of the procedure date.

Denominator

Expected number of in-hospital deaths for patients who have received surgery for colorectal cancer. Any inpatient with a primary procedure of one of the following OPCS codes:

  • H04 Total excision of colon and rectum
  • H05 Total excision of colon
  • H06 Extended excision of right hemicolon
  • H07 Other excision of right hemicolon
  • H08 Excision of transverse colon
  • H09 Excision of left hemicolon
  • H10 Excision of sigmoid colon
  • H11 Other excision of colon
  • H13 Bypass of colon
  • H15 Other exteriorisation of colon
  • H29 Subtotal excision of colon
  • H33 Excision of retum

Equivalent to “Excision of colon and/or rectum” procedure group in the DFI tools

And a primary diagnosis of one of the following ICD10 codes:

  • C18 Malignant neoplasm of colon
  • C19 Malignant neoplasm of rectosigmoid junction
  • C20 Malignant neoplasm of rectum
  • C218 Malignant neoplasm, overlapping lesion of rectum, anus and anal canal

Data Source

SUS – CDS

Time frame

April 2010 – March 2011

Basis

Acute trust

Statistical methods used

Expected counts are derived from logistic regression, adjusting for:

  • Sex
  • Age on admission (in five year bands up to 90+)
  • Admission method (non-elective or elective)
  • Socio-economic deprivation quintile of the area of residence of the patient (based on the Carstairs Index)
  • Procedure subgroup
  • Co-morbidities (Dr Foster methodology)
  • Number of previous emergency admissions in last 12 months
  • Year of discharge (financial year)
  • Palliative care (if any episode in the spell has the treatment function code 315 or contains ICD10 code Z515 in any of the diagnoses fields)
  • Month of admission
  • Source of admission

Logistic regression

The ratio is calculated by dividing the actual number of readmissions by the expected number and multiplying the figure by 100. It is expressed as a relative risk, where a risk rating of 100 represents the national average. If the trust has a SRR of 100, that means that the number of patients who were readmitted is exactly as would be expected taking into account the standardisation factors. A SRR above 100 means more patients were readmitted than would be expected; one below 100 means that fewer than expected were readmitted.

Control limits

Control limits tell us the range of values which are consistent with random or chance variation. Data points falling within the control limits are consistent with random or chance variation and are said to display ‘common-cause variation’; for data points falling outside the control limits, chance is an unlikely explanation and hence they are said to display ‘special-cause variation’ – that is, where the trust’s rate diverges significantly from the national rate.

Data points falling above the upper 99.8% control limit are said to be significantly ‘higher than expected’, data points falling below the lower 99.8% control limit are said to be significantly ‘lower than expected’, otherwise ‘within expected range’.

Notes

ICD10 contains no TNM staging information therefore we have tried to reproduce the essence using primary and secondary diagnosis fields. ‘Local spread’ requires the presence of a code for a local lymph node AND the absence of codes for distant nodes or organs. ‘Distant spread’ requires the presence of a code for distant nodes or organs (there may also be codes for local node or organ involvement present).

The denominator procedure group “Excision of colon and/or rectum” will be organised into the following procedure subgroups within the DFI tools and for the purposes of risk adjustment. This indicator is a collation of the first 6 subgroups.

Subgroup title Primary diagnosis codes Secondary diagnosis codes
1. Colon only, no nodes C18 No other C
2. Colon only, local nodes C18 C772 (intra-abdominal nodes) and no other
C77-C79
3. Colon only, distant spread C18 C77-C79 excl C772
4. Rectum involved, no nodes C19 or C20 or C218 No other C
5. Rectum involved, local nodes C19 or C20 or C218 C775 (intrapelvic nodes) and no other C77-C79
6. Rectum involved, distant spread C19 or C20 or C218 C77-C79 excl C772 if colon is also involved (i.e. primary diagnosis = C18 or C19) and also excl C775 if cancer confirmed to rectum (i.e. primary diagnosis = C20 or C218)
7. Cancer (not originating in colon or rectum) C00-C99 other than C18, C19, C20, C218;
D00-D09 (carcinoma in situ);
D37-D48 (neoplasms of uncertain or unknown behaviour)
Any
8. Other diseases (not cancer)   Any

Comment from the Dr Foster Hospital Guide Team

We suggest further refining the table above to provide greater definition. The new codes would be:

Subgroup title Primary diagnosis codes Secondary diagnosis codes
1. Colon, no spread C18 Any other than C19, C20, C218, C77-C79, D011, D012 (ca in situ in rectosigmoid junction or rectum)
2. Colon, local spread C18 Any of: C772 (intra-abdominal nodes) and no other C77-C79; C19, C20 or C218; D011, D012
3. Colon, distant spread C18 Any of: C77-C79 excl C772
4. Rectum with or without colon, no spread C19 or C20 or C218 No C77-C79
5. Rectum with or without colon, local spread C19 or C20 or C218 Any of: C775 (intrapelvic nodes) if no other C77-C79; C772 and no other C77-C79 if C19 is the primary dx
6. Rectum with or without colon, distant spread C19 or C20 or C218 C77-C79 excl C772 if colon is also involved (i.e. primary diagnosis = C19) and also excl C775 if cancer confirmed to rectum (i.e. primary diagnosis = C20 or C218)
7. Carcinoma in situ or cancer not originating in colon or rectum C00-C99 other than C18, C19, C20, C218;
D00-D09 (carcinoma in situ)
Any
8. Other diseases (not cancer) Any other than C and D00-D09 Any

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