Overall, the percent of children with "attention problems" indicated on the survey is higher than the percent with ADHD in the claims data for all age groups. It is difficult to determine why this is so. It is possible that parents are likely to report attention problems before children are diagnosed, or it may be that parents with children who have attention problems or are health care utilizers were more likely to complete the survey.

To compare the two sources of data directly, results were gathered for those for whom we had both a survey and encounter data--a total of 2,149 individuals. Results from the survey data were then compared to the encounter data. Of the 2,149 cases, 62 had a diagnosis of ADHD in the encounter data and 200 were reported to have attention problems on the survey. Table 7 provides a summary of the comparison indicating the agreement rates between the survey and encounter data.

Table 7. Survey and encounter data rate of agreement

	Problems with attention reported on survey	No problems with attention reported on survey	Total
ADHD diagnosis on encounter	43 (72%) a	17 (28%) b	60 (100%)
No ADHD diagnosis on encounter	157 (7%) c	1,930 (93%) d	2,087 (100%)

Cells a and d in Table 7 indicate agreement between the survey and the encounter data. Ninety-three percent (n=1,930) of the time when there was no ADHD diagnosis in the encounter data parents also did not report any attention problems, while 72% (n=43) of the time when there was an ADHD diagnosis in the encounter data parents did report attention problems. Cells b and c indicate areas of disagreement between the two data sources. Almost 30% of children (n=17) with an ADHD diagnosis in the encounter data were not reported as having attention problems by their parents, while 7% of children (n=157) without an ADHD diagnosis in the encounter files were reported as having attention problems.

ADHD diagnosis is still a rare occurrence, despite the fact that it occurs in up to 15% of the population. It is not difficult to imagine that parents may report attention problems prior to actually seeking medical intervention. It could also be that parents are reluctant to label their children as having attention problems There are also issues regarding differences in how the survey question was asked and how an encounter is coded that could have produced differences. For example, the survey question specifically asked if the child currently had a problem that had lasted at least the past 3 months. Some parents may not have indicated that the child had a problem currently because their symptoms were being controlled by an intervention. Another hypothesis is that the timing of the survey resulted in parents being asked about attention problems before children were actually diagnosed. This is unlikely since the encounters for ADHD were within the year prior to the survey for over 97% of the encounters. Regardless, it is important to know that differences in prevalence rates can occur when using encounter data and survey data.

Children with ADHD identified through filled prescriptions

Presentation of the above results to the Clinical Advisory Committee led members and researchers to question whether there were children within the population who were prescribed medications for ADHD but had not had an encounter within the year with a diagnosis code of ADHD. Children with at least one filled prescription for an ADHD-specific medication (see list below) were considered as having ADHD. Of 652 children with a filled prescription for an ADHD medication, 331 also had an encounter with ADHD as the diagnosis. Nearly half (321) did not have an encounter with ADHD as the diagnosis. Additionally, 40% of children with an encounter listing ADHD as the diagnosis did not have a filled prescription for an ADHD medication. When both diagnosis code and filled prescription are used to find children with ADHD, the number of children with ADHD increases from 563 to 884 (see Table 8).

The ADHD-specific medications included in our analysis were

•  Adderall

•  Cylert

•  Dexedrine

•  Methylphenidate hydrochloride

•  Pemoline

•  Ritalin

•  Strattera

Table 8. Children and adolescents enrolled for at least one month
by age and rate of ADHD, 2001
(includes children identified by filled prescription)

Age group	Number with ADHD	Total number	Percent with ADHD
3-6 years	73	4,751	1.5%
7-9 years	249	3,675	6.8%
10-12 years	295	3,491	8.5%
13-15 years	199	2,948	6.8%
16-18 years	68	2,296	3.0%
Total	884	17,161	5.2%

The addition of children with a filled prescription for an ADHD-specific medication increases the percentage of children with ADHD by about one-third across all age groups. Table 9 indicates the age and rate of ADHD for children who were eligible for at least 11 months. The rate of ADHD is greater in this table than in Table 2 due to the addition of children with a filled prescription for an ADHD-specific medication. Rates in Table 9 more closely resemble national rates for ADHD by age.

Table 9. Children and adolescents eligible for at least 11 months
by age and rate of ADHD, 2001
(includes children identified by filled prescription)

Age group	Number with ADHD	Total number	Percent with ADHD
3-6 years	27	1,230	2.2%
7-9 years	97	1,039	9.3%
10-12 years	126	1,033	12.2%
13-15 years	87	892	9.8%
16-18 years	31	752	4.1%
Total	368	4,946	7.4%

Table 10 provides information on ADHD rates by age and gender. Though the rate of ADHD increases for all age and gender groups, the pattern remains the same: boys are identified as having ADHD three times as often as girls.

Table 10. Rate of ADHD by age and gender for all enrollees, 2001
(includes children identified by filled prescription)

Age group	Gender	Number with ADHD	Total Number	Percent with ADHD
3-6 years	Female	11	2,309	0.5%
	Male	62	2,442	2.5%
7-9 years	Female	72	1,802	4.0%
	Male	177	1.873	9.5%
10-12 years	Female	71	1,717	4.1%
	Male	224	1,774	12.6%
13-15 years	Female	50	1,435	3.5%
	Male	149	1,513	9.8%
16-18 years	Female	16	1,166	1.4%
	Male	52	1,130	4.6%
Total	Female	220	8,429	2.6%
	Male	664	8,732	7.6%