Concept: International Classification of Disease (ICD) Coding in MCHP Data

Introduction

The International Classification of Disease (ICD) is a standard method of classifying and coding diagnoses, medical conditions and surgical procedures. Over time, different versions of this classification system have been used, captured and retained in several files in the Manitoba Population Research Data Repository (Repository) .

The following information identifies five sets of data in the Repository that capture ICD diagnoses and/or procedure codes, lists important time frames associated with different versions of ICD, provides notes on what is captured for each set of data, and lists comments specific to each set of data. The five sets of data include:


1. Diagnoses Codes on Medical Services (Physician Claims)
   
   
2. Diagnoses and Procedure Codes on Hospital Discharge Abstracts
   
   
3. Diagnoses Codes on Long Term Care (LTC) - (admission or separation)
   
   
4. Diagnoses Codes on Mental Health Management Information System (MHMIS) and
   
   
5. Diagnoses Codes on Vital Statistics Cause of Death

1 - Diagnoses Codes on Medical Services (Physician Claims)

This includes medical, reciprocal and non-statistical.



Time Frame	ICD Version Captured	Notes
1970/01/01 to 1972/02/28	ICD-7	* captured using 3-digit code, but Manitoba Health added 3-digit ICDA-8 code using a crosswalk table. * the ICD-7 code is present in the field later used for National Grouping Code (NGC).
1972/03/01 to 1979/02/28	ICDA-8	* captured using 3-digit code.
1979/03/01 to present	ICD-9-CM	* captured using 3-digit code. * In December 2018, a 5-digit diagnosis code variable was added to the Medical Services data. If recorded, the first 3-digits of both the 3-digit and 5-digit diagnosis code variables will match exactly. The 5-digit diagnosis code variable applies to records from 2015/16 forward.

Comments:

• Dates refer to when a claim was processed not the service date.
  
• In Manitoba, diagnosis codes also include the series "Ann","Bnn" or "Cnn" which are unique to Manitoba Health (prosthetics, Chiropractors, etc).
  
• No current plan exists for changing to ICD-10-CA. Some jurisdictions, including CIHI, are seriously considering changing to a comprehensive clinical terminology system called SNOMED (Systematized NOmenclature of MEDicine). See Wikipedia - https://en.wikipedia.org/wiki/Systematized_Nomenclature_of_Medicine for more information on SNOMED.

2 - Diagnoses and Procedure Codes on Hospital Discharge Abstracts

Time Frame	ICD Version Captured	Notes
1970/01/01 to 1979/03/31	ICDA-8	* 1-3 diagnoses and 1 separate external cause of injury codes (E-Codes) . * All coded using 4-digit ICDA-8. * DX01 is primary diagnosis. * 0-3 procedures coded using 4-digit ICDA-8. * Out-of-province and out-patient claims have 0-3 diagnoses and 0-1 procedure. 60% of claims in this era are Outpatient Department claims.
1979/04/01 to 1987/03/31	ICD-9-CM	* 1-16 diagnoses coded using 5-digit ICD-9-CM. * DX01 is primary diagnosis. * external cause of injury codes (E-Codes) not captured. * 0-12 procedures coded using 4-digit ICD-9-CM. * Out-of-province admissions and non-budget out-patient claims have 0-3 diagnoses and 0-1 procedure.
1987/04/01 to 2004/03/31	ICD-9-CM	* 1-16 diagnoses coded using 5-digit ICD-9-CM. * DX01 is most responsible diagnosis. * DXTYPE01-DXTYPE16 now exist. * Diagnosis #2 thru 16 can be external cause of injury codes (E-Codes) . * 0-12 procedures coded using 4-digit ICD-9-CM. * Out-of-province admissions and non-budget out-patient claims have 0-3 diagnoses and 0-1 procedure.
2004/04/01 to present	ICD-10-CA	For hospital admissions and day surgery in Manitoba Facilities: * 1-25 diagnoses coded using ICD-10-CA. * DX01 is most responsible diagnosis. * CIHI-based conversion to ICD-9-CM is also present for the 25 diagnoses but unreliable. * 0-20 procedures coded using Canadian Classification of Health Interventions (CCI).
2004/04/01 to present	ICD-9-CM	For admissions out of province (Reciprocal or not) and non-budget outpatient contacts: * 1-3 diagnoses coded using 5-digit ICD-9-CM. * DX01 is most responsible diagnosis. * DX02 and DX03 can be external cause of injury codes (E-Codes) . * 0-1 procedures coded using ICD-9-CM.

Comments:

• Dates refer to when a claim was processed not the service date.

3 - Diagnoses Codes on Long Term Care (LTC)

This includes admissions or separations.



Time Frame	ICD Version Captured	Notes
1973/04/01 to 1979/03/31	ICDA-8	* 1-3 Admit and 1-3 Separation diagnoses using 4-digit ICDA-8 code.
1979/04/01 to 2004/06/01	ICD-9-CM	* data collects 1-3 Admit and 1-3 Separation diagnoses using 5-digit ICD9-CM. * existing ICDA-8 diagnoses were retained and modified by adding a trailing "$" symbol in the 5th digit.
2004/06/01 to present	ICD-9-CM or ICD-10-CA	* same as above plus new information may be recorded using ICD-10-CA diagnoses codes.

Comments:

• In the LTC system, diagnoses are captured using the prevalent ICD system in use at a facility at the time. Typically, LTC facilities attached to a hospital use the same ICD version in use at the hospital.
• The LTC system at MCHP, at any given point, contains ALL information for 1973 through to the most recent fiscal year.
• A text variable for each diagnosis filed contains an ICD version qualifier: either "ICD-9-CM" or "ICD-10-CA".
• Some facility data may not follow the time frames outlined above because they did not begin using a different version until later in the time frame window.

4. Diagnoses Codes on Mental Health Management Information system (MHMIS)

Time Frame	ICD Version Captured	Notes
1990/04/01 to 2001/01/19	ICD-9-CM	* 1-3 diagnoses coded using 5-digit ICD-9-CM. * 1-5 diagnoses coded using DSM-III Axis codes. * data collected at registration and on status changes.
2001/01/20 to present	ICD-9-CM	* 1-3 diagnoses coded using 5-digit ICD-9-CM. * 1-5 diagnoses coded using DSM-IV Axis codes. * data collected at registration and on status changes.


Comments:

• DSM-III = Diagnostic and Statistical Manual of Mental Disorders, version 3
  
• DSM-IV = Diagnostic and Statistical Manual of Mental Disorders, version 4

5 - Diagnoses Codes on Vital Statistics Cause of Death

Time Frame	ICD Version Captured	Notes
1970/01/01 to 1978/12/31	ICDA-8	* cause of death and nature of injury are coded in ICDA-8.
1979/01/01 to 1999/12/31	ICD-9	* cause of death and nature of injury are coded in 4-digit ICD-9 (not the same as ICD-9-CM).
2000/01/01 to present	ICD-10	* W.H.O. standard coding for cause of death. * W.H.O. ICD-10 is not entirely compatible with ICD-10-CA.

Comments:

• Vital Statistics collects only one diagnosis for reporting the primary cause of death, with the possibility of several diagnoses codes related to the underlying cause of death. In data from 2000 forward, the number of variables for reporting underlying cause of death increased from one to twenty.
• Vital Statistics reporting is based on the calendar year, not the fiscal year.

MORE INFORMATION

• Information for this concept was extracted from an e-mail from Pat Nicol to Souradet Shaw - August 29, 2006