Appendix: Operational Definitions for Clinical and Laboratory Variables
Operational definitions
Criteria
Severe depression
Any hospital admission with a diagnosis of depression OR 2 outpatient
visits with diagnosis of depression. Must have occurred prior to HCV
treatment in patients who received treatment.
Severe hypertension
One inpatient ICD 9 code for malignant hypertension or hypertension with
complications
Severe heart failure
One inpatient ICD9 code OR 2 outpatient codes for CHF
Significant coronary
Any inpatient ICD9 code for coronary artery disease OR
artery disease (CAD)
coronary revascularization procedure
Poorly controlled
2 inpatient or outpatient I-CD9 codes for diabetes with complications > 1
diabetes
month apart
Severe COPD
Any inpatient ICD9 code for COPD with an ICD9 code for respiratory
failure
Drugs abuse
Inpatient primary ICD9 OR 2 outpatient ICD9 codes for drug
dependence/abuse
Alcohol abuse
Inpatient primary ICD9 code for alcohol OR 2 outpatient ICD9 codes for
alcohol dependence/abuse
HIV co-infection
Any positive blood test (antibody, Western blot, or viral load) or ICD-9
code for HIV
Cirrhosis
Any ICD-9 code for cirrhosis or its complications (ascites, varices,
encephalopathy, hepatitis w/coma, and portal hypertension) in inpatient or
outpatient files.
Liver transplant
recipients
Any inpatient or outpatient ICD 9 code for liver transplant
Anxiety/PTSD
Any primary inpatient ICD9 code for anxiety/PTSD
Bipolar
Any primary inpatient ICD9 code for bipolar disorder
Psychosis
Any primary inpatient ICD9 code for psychosis
Non-metastatic cancer
Any inpatient or outpatient ICD-9 code for non-metastatic cancer during
the entire time before the HCV index date and two years after.
Highest creatinine
Highest lab value in the two years before or after the HCV index date. For
patients who received HCV treatment the highest value before treatment.
Lowest hemoglobin,
Lowest lab value in the two years before or after the HCV index date. For
white blood cell count,
patients who received HCV treatment the lowest value before treatment.
and platelet count
Elevated ALT
ALT >40 IU/ml for all tests within the two years prior and two years after
HCV index date
HCV Genotype
Genotype 1 or 4, 2 or 3, or not tested.
For ICD-9 codes, we used the AHRQ Clinical Classification System to classify all patient ICD9 codes into the
relevant diagnosis. With the exception of variables with timing mentioned above, variables were defined as the
presence of the code two years before or two years after the HCV index date.