APPENDIX
Sample Selection
Drawing from similar methods that we used in our prior work that
assessed trends in management of back pain,1 we used the NAMCS and
NHAMCS Reason for Visit Classification for Ambulatory Care codes2 to identify
three related reasons for visit (RFV) including Headache/pain in head, Migraine
headache, and Tension headache. We then used ICD-9-CM codes to identify
additional visits where a diagnosis of headache or migraine was made. Relevant
diagnoses that were available in the NAMCS and NHAMCS ICD-9-CM diagnostic
lists are outlined in Table A1. We also used the following NAMCS/NHAMCS
reason for visit codes to identify clinical red flags, which would indicate
something other than routine headache. We excluded these from the analysis.
These included fever, disorders of speech/speech disturbance, slurring,
convulsions, altered level of consciousness, epilepsy, and HIV with or without
associated conditions. Table A2 summarizes the clinical red flags represented by
ICD-9-CM codes, which served as additional exclusion criteria.
We summarize cohort design in Appendix Table A3. Based on the above
reasons for visits and diagnosis codes, we created five groups of patients
presenting with headache. Our first group was the gold standard group, which
consisted of patients who presented with new onset (<3 months duration) or
acute on chronic headache. Our second group consisted of patients with nonprimary complaints and non-primary diagnoses of headache. The third group
consisted of patients who presented with a chief complaint of headache, which
was not acute. The fourth group consisted of patients who only presented with a
primary diagnosis of headache, but not a chief complaint. Groups 1-4 excluded
any patients with potentially competing diagnoses, such as back pain, abdominal
pain, joint pains, which could potentially confound utilization trends of the key
outcomes we studied. Finally, group 5 included groups 1-4 and added in visits
with competing diagnoses. The groups were mutually exclusive. When we
compared trends in group 1, our gold standard group, with the other groups,
trends were similar. We therefore include in our primary results all groups.
Main Outcomes
As previously described in our prior study on back pain,1 during the years
2001-2004, the CT/MRI variable was removed from the survey instrument, and
we substituted “other imaging” in its place. When we removed the years 20012004, the trend for CT/MRI remained unchanged (see Table A4); therefore we
kept them for the purposes of consistency and to maximize sample size. During
2007-2010, MRI and CT were reported separately so these were combined for
analyses to maintain consistency over the study period. The referral to other
physicians variable was presented as a binary checkbox on the survey
instrument during each year of the study. The counseling variable has several
subcategories, including dietary and nutrition education/counseling, exercise
education/counseling, and stress management and mental health
education/counseling. If any of these three types of counseling were checked off
for a given visit for headache, then our counseling variable was counted as
positive. We chose these particular subcategories of counseling because of the
substantial dietary, lifestyle, and psychosocial influences on migraine and
tension-type headaches in addition to specific guideline recommendations for
counseling.3-5
Competing Diagnoses
Table A5 illustrates unadjusted use over time after excluding visits with
competing diagnoses, which might confound trends in utilization. In this
sensitivity analysis, we excluded visits that included any of the following ICD-9CM codes: musculoskeletal disorders (711-719, 730-736), back pain (724)
abdominal diseases (540-543, 550-555, 574-577, 789), liver diseases (592, 594),
kidney stones (592, 594), any fracture (805-830), dislocation (831-839), sprains
and strains (840-848), encephalitis (323-326), dementia or degenerative nervous
system disease (330-341), stroke (342-345, 347-349), pneumonia (481-487).
Excluding these diagnoses revealed similar trends to our main analysis,
therefore, visits with these diagnoses were included in the primary analysis in
order to maximize sample size and power.
Clinical Guideline Selection
We performed a MEDLINE search and review of the National Guideline
Clearinghouse using search terms such as headache guidelines, migraine
guidelines, headache clinical practice guidelines, and migraine clinical practice
guidelines, appropriate use of imaging for headache. We identified three major
clinical headache guidelines that would most likely influence U.S. clinician
behavior during the study period. These three guidelines were released
proximate to the first half of the study period and were published by major
professional societies: The American College of Physicians for migraine in 2002,
the American Academy of Neurology for headache in 2000, and the Institute for
Clinical Systems Improvement for headache in 1998.3-5 Of note, although
verapamil was recommended during the study period, the American Academy of
Neurology Guideline 2012 update on pharmacologic prevention of migraine 6
finds unsatisfactory evidence for verapamil (conflicting and poor studies).
Amitriptyline went from 1 (proven efficacy; 2000) to B (probably effective; 2012),
while propranolol remained high (1 to A), and topiramate had a better evidence
base (3 to A).
Table A1. Inclusion Criteria According to Presence of ICD-9-CM Diagnostic Codes
ICD-9-CM Code
General Description
784.0
Headache
307.81
Tension Headache
346.00
346.01
346.10
346.11
346.20
346.80
346.81
346.90
346.91
Classical migraine without mention of intractable migraine
without mention of status migrainosus
Classical migraine with intractable migraine, so stated,
without mention of status migrainosus
Common migraine without mention of intractable migraine
without mention of status migrainosus
Common migraine with intractable migraine, so stated,
without mention of status migrainosus
Variants of migraine without mention of intractable migraine
without mention of status migrainosus
Other forms of migraine, without mention of intractable
migraine without mention of status migrainosus
Other forms of migraine, with intractable migraine, so
stated, without mention of status migrainosus
Migraine, unspecified, without mention of intractable
migraine without mention of status migrainosus
Migraine, unspecified, with intractable migraine, so stated,
without mention of status migrainosus
Table A2. Exclusion Criteria According to Presence of ICD-9-CM Diagnostic Codes
ICD-9-CM Code
801 - 804
345
General Description
Fracture of the skull or face
Epilepsy
850 - 854
Head Trauma
140-208
Malignancy
042 - 044
Human Immunodeficiency Virus and
associated complications
781 - 785
Neurologic Deficit (e.g., weakness)
V220-V222, V230-V235, V237-V240
Pregnancy and associated complications
Table A3. Cohort Design
Group
1
2
3
4
5
Description
Primary reason for visit due to new onset (<3
months duration) or acute on chronic
headache or migraine
Both non-primary complaint and non-primary
diagnosis of headache or migraine and
competing diagnoses are absent
Primary complaint of headache or migraine
during chronic routine, pre/post operative, or
general/preventative visit and without
competing diagnoses
Primary diagnosis of headache or migraine
without a complaint and without competing
diagnoses
Groups 1-4 and including competing
diagnoses
Sample n (%)
3,896 (41.6)
582 (6.2)
2,969 (31.7)
913 (9.8)
1,002 (10.7)
Table A4. Unadjusted Percentages of CT/MRI Use Excluding 2001-2004
Year (sample n)
CT/MRI
1999-2000
(n=1,299)
6.7
2005-2006
(n=1,533)
9.4
2007-2008
(n=1,579)
13.5
2009-2010
(n=1,585)
13.9
P-value
0.001
Table A5. Unadjusted Use over Time Without Competing Diagnoses (% of Visits)
1999-2000
(n=1,165)
2001-2002
(n=1,556)
2003-2004
(n=1,469)
2005-2006
(n=1,375)
2007-2008
(n=1,389)
2009-2010
(n=1,406)
P-value
Advanced Imaging
(CT/MRI)
6.5
6.9
7.0
9.1
12.6
14.6
<0.001
Referrals to Other
Physicians
7.0
8.9
10.7
10.1
12.4
11.9
0.01
Headache
Prevention
Counseling
21.7
22.6
23.0
19.2
14.7
18.1
0.044
NSAIDs/APAP
14.7
18.9
15.4
13.5
18.6
15.3
0.94
Triptans/Ergot
10.0
13.0
13.5
19.2
14.2
17.3
0.006
Preventative
Opioid/Barbiturate
9.0
19.2
9.5
15.8
10.4
20.1
12.1
17.1
13.2
20.1
15.9
18.9
0.003
0.74
Year (sample n)
Medications
Abortive
Abbreviations: NSAIDs, non-steroidal anti-inflammatory drugs; APAP, acetaminophen; Preventive:
propranolol, verapamil, amitriptyline, and topamirate; Headache Prevention Counseling: diet and nutrition
education/counseling, exercise education/counseling, stress management/mental health
education/counseling.
Table A6. Patient Visit Characteristics Over Time
Year (Sample n)
1999-2000
(n=1,299)
46.5
75.3
2001-2002
(n=1,717)
44.7
73.0
2003-2004
(n=1,649)
45.7
73.9
2005-2006
(n=1,533)
46.0
72.8
2007-2008
(n=1,579)
45.0
78.9
2009-2010
(n=1,585)
46.8
75.2
Age (mean)
Female Sex
Race/Ethnicity*
White
71.7
80.4
71.1
77.9
71.0
76.0
Black
9.8
9.1
12.2
9.1
14.6
12.0
Hispanic
12.8
6.9
12.5
8.7
9.6
7.9
Other
5.7
3.7
4.3
4.3
4.9
4.1
Insurance Status
Private
57.5
67.0
67.5
62.0
62.8
60.4
Medicare
13.0
10.5
14.0
13.0
11.6
16.8
Medicaid
10.3
7.4
9.0
11.2
10.7
12.1
Workers' Comp
2.6
1.1
0.81
0.25
0.80
1.4
Uninsured
13.4
9.2
7.2
6.4
11.7
7.4
Identified PCP
57.7
59.6
59.4
54.7
57.0
54.1
Metro Area
79.8
79.5
82.8
84.8
87.9
85.2
Region
Northeast
20.7
18.1
21.8
18.1
13.5
18.3
Midwest
23.2
22.3
17.8
29.7
21.3
26.9
South
30.7
35.1
40.6
32.6
42.7
34.5
West
25.4
24.5
19.9
19.5
22.5
20.4
Headache Chief
Complaints†
Acute or New
Onset
62.3
54.0
54.2
54.2
50.6
56.7
Chronic Routine
32.0
39.1
41.5
40.6
40.4
38.9
Pre/Post Operative
2.5
0.25
0.73
1.05
0.57
0.60
Preventative Care
2.0
1.9
2.3
2.2
3.8
3.5
* White, Black, and Other patients are all non-Hispanic in origin. Hispanic origin may include patients of
any race. Other race/ethnicity includes persons of Asian, Native Hawaiian, Pacific Islander, American
Indian, or multiple races.
† 80.8% of the sample comprises patients with a chief complaint of headache (proportions may not add to
100% due to the 1.7% missing values for this variable).
PCP primary care physician.
Pvalue
0.42
0.38
0.027
<0.001
.89
.67
.45
<0.001
Table A7. Adjusted* Proportions of Use by Identified PCP versus Non-PCP over Time
Year
1999-2000 2001-2002 2003-2004 2005-2006 2007-2008 2009-2010
(sample n, PCP)†
(n=519)
(n=496)
(n=511)
(n=522)
(n=511)
(n=543) P-value
[Sample n, non-PCP]
[n=680] [n=1,104] [n=1,037]
[n=929]
[n=969]
[n=933]
Advanced Imaging
(CT/MRI)
PCP
5.7
4.4
5.2
4.7
10.2
10.8
0.012
Non-PCP
6.9
7.6
8.8
16.2
15.5
15.7
<0.001
Referrals to Other
Physicians
PCP
5.2
8.1
11.3
8.9
12.9
11.0
0.022
Non-PCP
7.2
10.3
8.1
9.1
11.1
14.5
0.017
Headache Prevention
Counseling
PCP
27.6
26.5
22.8
27.1
18.1
19.7
0.028
Non-PCP
16.0
13.9
19.1
9.5
9.6
13.8
0.15
Medications
Abortive
NSAIDs/APAP
PCP
15.0
26.8
17.3
16.3
18.9
17.1
0.39
Non-PCP
12.6
13.2
15.2
10.0
15.0
14.3
0.65
Triptans/Ergot
PCP
8.3
13.9
10.2
14.4
14.1
16.3
0.43
Non-PCP
8.6
13.8
11.7
13.7
13.5
15.7
0.004
Preventative
PCP
7.8
7.0
9.4
9.8
8.0
12.7
0.13
Non-PCP
10.0
12.1
9.7
13.3
20.2
17.4
<0.001
Opioid/Barbiturate
PCP
18.0
16.2
22.2
18.6
18.4
17.9
0.97
Non-PCP
17.1
12.7
13.7
14.3
22.9
18.8
0.16
*In this table, our models adjusted for age, sex, race/ethnicity, region, insurance type, symptom
duration, and whether the visit was located in a metropolitan area.
† In this stratified analysis, the variable for PCP-status was missing unknown 6.5% of the time.
For this stratified analysis, we collapsed the worker’s compensation insurance variable into the
uninsured variable due to a lack of enough cells for the models to converge.
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