Sexually Transmitted Diseases among American Indians and Alaskan Natives in
Washington State, 1995–2000
Running head: STDs among AI/ANs in Washington
Emily Puukka, MS
i iShawn Jackson, BA iPaul Stehr-Green, DrPH, MPH
iThe Northwest Tribal Epidemiology Center, Northwest Portland Area Indian Health
Board, 527 SW Hall, Suite 300, Portland, Oregon 97201
Acknowledgements: The authors acknowledge the contributions of Mark Stenger, M.A.,
Epidemiologist, Washington State Infectious Disease and Reproductive Health
Assessment Unit, to the conceptualization and realization of this study.
Correspondence: Ms. Emily Puukka, Northwest Portland Area Indian Health Board, 527
SW Hall, Suite 300, Portland, OR 97201; e-mail: email@example.com; telephone: 503-228-4185; fax 503-228-8182
Reprints: Ms. Chandra Wilson, Northwest Portland Area Indian Health Board, 527 SW
Hall, Suite 300, Portland, Oregon 97201; e-mail: firstname.lastname@example.org; telephone: 503-228-4185; fax: 503-228-8182
Word counts: Text (3,153 words), References (315 words), Figures (4), Tables (1)
STDs among AI/ANs in Washington Page 2
Sexually transmitted diseases (STDs) occur in epidemic proportions in the United States, and the burden of disease is disproportionately high among American Indians and Alaskan Natives (AI/ANs). In the year 2000, AI/ANs reportedly had the second highest case rates of syphilis (2.6 per 100,000 population), chlamydia (680.2 per 100,000), and gonorrhea (114.4 per 100,000) nationally . To address this issue, the Department of Health and Human Services has designated STDs as one of its six special focus areas in its initiative to eliminate racial health disparities.
However, even these measures of the burden of STDs on AI/AN populations may be underestimated. Several studies suggest that racial misclassification of AI/ANs is a significant problem in many areas of the United States. Previous reports have shown that AI/ANs are substantially undercounted in vital statistics and other public health databases, including cancer registries [2-10]. Thus, uncorrected morbidity and mortality rates for AI/ANs are often spuriously low, which underestimate the true burden of disease on AI/AN populations. There are no published reports that examine the impact of racial misclassification on the ascertainment of STDs among Northwest AI/ANs. We, therefore, conducted this study to determine more accurate estimates for the incidence of STDs among AI/ANs living in Washington State.
The Northwest Tribal Epidemiology Center is a tribally operated program administered by the Northwest Portland Area Indian Health Board (NPAIHB). It was established in 1997 with the mission of providing Northwest tribes with timely, accurate, and useful health status information. A key part of this effort is the Northwest Tribal Registry (NTR) Project that was started in January 1999. The goal of the NTR is to improve the accuracy of health data for AI/ANs through linking the NTR with a variety of health data sets. These data sets contain health data for Northwest AI/ANs, but may not have racial identifiers or may have inaccurate racial identifiers. The NTR is an enumeration of
AI/ANs primarily from Idaho, Oregon, and Washington. Source data for the NTR come from the Portland Area Indian Health Service (IHS) Area Patient File, a compilation of
patient demographic data from Indian health care facilities that use the Resource and Patient Management System (RPMS) and export patient data to the Portland Area IHS Office. RPMS data represent individuals who received services from Northwest Indian health care facilities from the mid-1980s to the present. All individuals in the NTR are of proven AI/AN ancestry and have accessed health services from an IHS or tribal healthcare facility during this time period. The NTR was rigorously standardized and cleaned for use in this linkage project. The Washington State Department of Health (WADOH) STD Registry included data for years 1995–2000. Prior to the linkage study,
this data set was standardized for linkage variables and diagnostic information. We received approval to conduct this linkage study from both the Portland Area IHS
STDs among AI/ANs in Washington Page 3
Institutional Review Board (IRB) and the IHS Headquarters-Albuquerque Area Combined IRB.
The version of the NTR used to conduct this linkage included 165,332 AI/ANs. This file contains approximately 12,700 duplicate records which were retained for the purpose of linkage in an effort to increase the likelihood of a match. The file was derived from the Portland Area RPMS, a decentralized automated information system that is used by
Indian health care facilities (with the exception of the Seattle Indian Health Board) in Idaho, Oregon, and Washington.
The WADOH STD Registry file (WADOH STD) represented 76,447 patients who had been diagnosed with STDs during 1995-2000. The file includes data on a total of 101,745 cases of STDs, including all cases of gonorrhea (n = 13,239), chlamydia (n = 64,251), syphilis (n = 998), and other STDs (genital herpes, pelvic inflammatory disease [PID], and nongonoccocal urethritis) (n = 23,257) reported to the state between 1995-2000. We have limited our subsequent analysis and discussion of STDs to include only cases of gonorrhea and chlamydia.
The NTR-WADOH STD linkage was conducted using the record linkage software INTREGRITY? (Ascential Software, 2002), which employs probabilistic record linkage
algorithms. This software is designed to match records in two different data files for individuals for whom data on selected fields (i.e., name, date of birth, social security number) are contained in both files. The software identifies not only ―deterministic‖ matches where the fields of interest are exactly identical between the two files, but also calculates the probability of a true match in situations where there are minor differences between the two records (e.g., transposed digits in a social security number or misspellings of a name).
The NTR and WADOH STD files were linked using the following fields:
? first and last name
? middle initial
? month, day, and year of birth
The record linkage was conducted in a six-pass run, each pass designed to allow errors on some fields, but not on others. In succeeding passes, matching combinations were alternated so that after six rounds, all plausible matches were obtained using the available fields. The initial error rates for each pass were given wide margins, and then recalibrated as necessary to minimize false-positive matches. Clerical review (i.e., case-by-case examination of questionable matches) helped to further clarify and separate true matches from false matches. Although not included in the actual matching criteria,
STDs among AI/ANs in Washington Page 4
additional fields available in both datasets, (i.e., city and zip code of residence), were
used in the clerical review process.
Upon completion of the linkage, results were extracted for data analysis using SPSS?
and UltraEdit 3.2?. All identifying fields were permanently removed from the new files
created by the linkage; however, a unique key index number was created and attached to
each linked record to allow easier repeat linkage if needed later to examine additional
Definition of Terms
? Matched AI/AN case – a reported STD case for which the individual was
identified in both the NTR and the WADOH STD Registry.
? Race correctly classified – a matched case for which the WADOH STD Registry
correctly identifies the individual as AI/AN.
? Race incorrectly classified – a matched case for which the WADOH STD
Registry incorrectly identifies the individual as non AI/AN (any race other than
? Unmatched AI/AN case – a reported STD case for which the individual was
identified as AI/AN in the WADOH STD Registry, but did not match with any
individual in the NTR. We included these cases in our analysis of demographic
characteristics and disease-specific comparisons.
Prior to 2000, US censuses allowed for the reporting of only one race, whereas in 2000
respondents were allowed to self-report one or more races from the following: White,
Black or African American, American Indian or Alaska Native, Asian Indian, Chinese,
Filipino, Japanese, Korean, Vietnamese, Native Hawaiian, Guamanian or Chamorro,
Samoan, Other Asian, Other Pacific Islander or ―Some Other Race‖. Thus, because this change in the way race is self-designated occurred in the midst of our study period (1995-
2000), determining appropriate denominators for calculating race-specific rates of disease
presented some methodologic challenges.
For the year 2000 denominators, we used Washington State population data from the
2000 US Census for total AI/ANs (n=158,945), which includes individuals who self-
reported as ―AI/AN only‖ (n=93,301, or 58.7% of the total number of AI/ANs) and
individuals who self-reported as ―AI/AN in combination with one or more other race(s)‖
(n=65,644, or 41.3%). We calculated the denominator for Whites in a similar fashion,
including persons who self-reported as ―White only‖ and White in combination with one
or more other race(s)‖.
To estimate comparable denominators for 1995-1999, we used the Washington State
Office of Financial Management (OFM) 1995 race-specific intercensal population
STDs among AI/ANs in Washington Page 5
estimates as the basis for further adjustment and extrapolation. For 1995, the Washington OFM estimated there were 88,005 AI/ANs living in Washington State. Assuming that
this estimate was analogous to the 93,301 individuals who self-reported ―AI/AN alone‖ in the 2000 US Census, and that this group comprised 58.7% of the total AI/AN
population during 1995-1999 (i.e., the same proportion of persons who self-reported as
―AI/AN alone‖ out of the total number of AI/ANs reported in the 2000 census), we
estimated that there was a total AI/AN population of 149,923 (i.e., composed of 88,005
who would have self-reported as ―AI/AN alone‖ and 61,918 who would have self-
reported as ―AI/AN in combination with one or more other race(s)‖. Then, given that the
estimated overall percentage increase in the AI/AN population from 1995 to 2000 was 6
percent (corresponding to an absolute increase of 9,017 AI/AN individuals), we
apportioned this increase equally over the 5 years (95-96, 96-97…99-00), which resulted in the incremental addition of 1,803 to the number of AI/AN individuals per year.
Furthermore, we assumed that the distribution of AI/AN subgroup populations (i.e., by
age group and sex) was relatively stable from 1995-2000, and applied the age and sex
distributions reported in the 2000 census for the total AI/AN population to each of the
1995-1999 estimates. Finally, in order to have denominators for the 1995-1999 White
population that were derived using identical methodology (and thereby make STD rates
among AI/AN and white populations comparable), we repeated the entire process
outlined above to the OFM estimates for the White population of Washington State.
We linked the 1995-2000 WADOH STD
file representing 77,490 cases of Figure 1. AI/AN STD Cases, chlamydia and gonorrhea with the Washington State, 1995-2000 165,332 AI/AN records in the NTR. In (N=3,235)so doing, we identified matches for Matched,2,058 AI/AN chlamydia and gonorrhea coded asAI/ANcases, including 1,320 (or 64.1% of the (n=1,320)2,058 matched cases) that were Matched,36%identified as AI/AN in both the NTR and 41%coded as non-in the WADOH STD files and 738 AI/AN (n=738)
(35.9% of the matched cases) which
Not matched,were misclassified as non-AI/AN in the coded asWADOH STD files (Figure 1). In AI/ANaddition, there were 1,177 chlamydia and gonorrhea cases for which race was recorded as (n=1,177)23%AI/AN in the WADOH STD files, but that did not match any record in the NTR. Thus,
by virtue of the linkage with the NTR, we were able to identify a total of 3,235
chlamydia and gonorrhea cases diagnosed among AI/ANs during 1995-2000 (i.e.,
comprising 738 newly identified AI/AN cases, in addition to the 2,497 cases that were
originally identified as AI/AN in the WADOH STD files), for an increased ascertainment
of just over 29%. Overall, AI/ANs accounted for 4.2% of the 77,490 cases of chlamydia
and gonorrhea reported to WADOH during 1995-2000.
STDs among AI/ANs in Washington Page 6
These 3,235 cases of chlamydia and gonorrhea occurred among a total of 2,489 AI/AN
persons during the six-year time period (i.e., 2,661 cases of chlamydia only, 288 cases of
gonorrhea only, and 143 of these persons were diagnosed with both chlamydia and
gonorrhea between 1995 and 2000). The results of the remaining analyses presented
below will focus on the number of cases of STDs, as opposed to the number of persons
diagnosed with STDs during 1995-2000 in Washington State.
In all, 22.8% (738 of 3,235) of the AI/AN cases were originally misclassified as non-
AI/AN in the WADOH files. With regard to the patterns of misclassification, female
AI/ANs were equally as likely as males to be misclassified as non-AI/ANs in the State
database (21.6% versus 22.8%, respectively). Similarly, AI/AN persons living in urban
areas at the time of their diagnosis with an STD were slightly less likely to be
misclassified (20.7% of urban residents versus 22.2% living in rural areas). There was a
strong, statistically significant inverse association between blood quantum (i.e., a
measure of AI/AN ancestry) and misclassification: AI/AN persons with a 100% blood
quantum were about one-fourth as likely to be misclassified as AI/AN persons with less
than 25% level of AI/AN ancestry (16.2% misclassification among persons with full
blood quantum versus 56.7% misclassification rate among persons with <25% blood
quantum). With regard to the age-specific rates of misclassification (Figure 2), the
highest rates occurred among the age groups at highest risk for STDs—viz., 15-19 year
olds (26.1% were misclassified), 20-24 year olds (20.9%), and 25-29 year olds (21.9%).
An annual average number of 540 STD cases were diagnosed among AI/ANs throughout
the six years between 1995 and 2000, but there was a slight increase in the annual
number of AI/AN persons diagnosed throughout the time period (i.e., ranging from 480
cases in 1997 to 615 cases in 2000), and this temporal trend is similar to that for STD
cases among Whites in Washington during the same time period (Figure 3). Similarly,
the annual age-
appear to have Figure 2. Racial Misclassification of AI/AN Gonorrhea and Chlamydia remained fairly Cases by Age, Washington State, 1995-2000
steady 96.0Correctly classifiedMisclassifiedthroughout this 84.581.810080.680.579.579.178.1time period for 73.390both AI/ANs 80and Whites, at 70the same time 60
50that age-26.721.94020.919.419.5adjusted rates 20.515.518.230of chlamydia Percentage of cases4.020appear to have 10increased for 00-910-1415-1920-2425-2930-3435-3940-4445+
STDs among AI/ANs in Washington Page 7
both race groups. However, AI/AN appeared to be at greater risk than Whites for both
chlamydia and gonorrhea in all years, based on comparison of annual race-specific age-
adjusted rates between 1995 and 2000.
Figure 3. Annual Number and Age-adjusted Rates of STD Cases in Washington,
1995–2000, by Race
STDs in AI/AN--Washington, 1995-2000STDs in Whites--Washington, 1995-2000
800400.08000400.0600300.06000300.0400200.0cases4000200.0casesraterateNumber of 200100.0Number of 2000100.0Age-adjusted Age-adjusted 00.000.0199519961997199819992000199519961997199819992000Year of DiagnosisYear of diagnosis
Number of STD cases among AI/ANNumber of STD cases among WhitesChlamydia age-adjusted rate (per 100,000)Chlamydia age-adjusted rate (per 100,000)Gonorrhea age-adjusted rate (per 100,000)Gonorrhea age-adjusted rate (per 100,000)
NOTE: Whereas the magnitude and range of values in the right-hand axes representing the crude
rates of STDs are exactly the same for Whites and AI/AN, the left-hand axes representing the absolute number of cases are different—with that for Whites being an order of magnitude higher. Also, because AI/AN were generally younger than Whites in Washington (estimated median age = 27.8 years versus 36.7 years, respectively), we indirectly adjusted rates to the 2000 U.S. total population.
Of the 3,235 AI/AN cases, 2,669 (82.5%) were among females, compared with 30,927 of
40,883 (75.6%) for Whites during this time period (Table 1). For reported cases of
gonorrhea, 70% of the cases among AI/AN occurred in females, compared to only 50%
of the cases among Whites; the sex-specific distribution of chlamydia cases was
equivalent for AI/AN and Whites, with about 80% of cases occurring among females.
Overall, AI/ANs are at greater risk of both of these STDs than their White counterparts:
the average annual age-adjusted incidence rates for gonorrhea and chlamydia for both
sexes combined are two times higher for AI/ANs compared with Whites; furthermore,
AI/AN females appear to be at even higher risk than their White counterparts for
gonorrhea—the age-adjusted incidence rate among AI/AN females is about 2.8-fold
higher than that among White females. In contrast, the increased risk for AI/AN males
compared with White males appears to be somewhat lower for both chlamydia (about
67% higher age-adjusted rate among AI/AN males) and gonorrhea (about 50% higher
STDs among AI/ANs in Washington Page 8
Table 1. Average Annual Number of STD Cases and Age-adjusted Incidence Rates*, by Sex and Race, 1995-2000 Cases Age-adjusted Cases Age-adjusted Cases Age-adjusted
Females Males Both Sexes Rate Rate Rate
(per 100,000) (per 100,000) (per 100,000) STD Race
50 56.6 22 28.4 72 41.1 AI/ANs
464 20.1 466 19.2 930 19.5 Whites
395 434.3 73 82.8 467 256.4 AI/ANs
4691 202.4 1193 49.5 5884 123.9 Whites
NOTE: *-Because AI/AN were generally younger than Whites in Washington (estimated median age = 27.8
years versus 36.7 years, respectively), we indirectly adjusted rates to the 2000 U.S. total population.
For those STD cases reported in Washington during 1995-2000 for which age at
diagnosis was known, AI/AN case-patients were only slightly younger than White case-
patients: over this 6-year period, the average estimated median age at diagnosis of
chlamydia was 20.4 years for AI/AN vs. 21.1 years for Whites; for gonorrhea, it was 22.5
vs. 24.8, respectively. Of the 3,195 AI/AN cases for which age was known at time of
diagnosis, 2,685 (84%) were among adolescents and young adults (viz., 15–29 years of age), compared with 33,495 of 39,977 (84%) among Whites. Of note, AI/AN
experienced a higher attack rate for both chlamydia and gonorrhea in virtually every age
group (Figure 4).
Figure 4. Average Annual Age-specific Rates of STDs in Washington, 1995–2000, by Race
Chlamydia--Washington, 1995-2000Gonorrhea--Washington, 1995-2000
140014012001201000100WhitesWhites80080600AI/ANAI/AN60400402002000Age-specific rate (per 100,000)Age-specific rate (per 100,000)<10<10'10-14'10-14Age GroupAge Group'15-19'15-19'20-24'20-24NOTE: The magnitude and range of values in the left-hand axes representing the age-specific rates of '25-29'25-29DISCUSSION cases are different—with that for chlamydia being an order of magnitude higher. '30-34'30-34'35-39'35-39 '40-44'40-44>45 >45
STDs among AI/ANs in Washington Page 9
This study describes racial misclassification of AI/ANs in the Washington STD files during the years 1995–2000. As a result of the probabilistic linkage of the State’s files
with the NTR, we were able to identify a total of 3,235 chlamydia and gonorrhea cases diagnosed among AI/ANs during 1995-2000 (i.e., comprising 738 newly identified AI/AN cases, in addition to the 2,497 cases that were originally identified as AI/AN in the WADOH STD files), for an increased ascertainment of just over 29%.
Based on these data, it appears that the majority of STD cases are occurring among 15-30 year olds of all races; however, AI/ANs in this high-risk age group appear to be affected at about twice the rate as Whites in Washington. This racial difference is larger among female AI/ANs compared to White females in Washington, but this may be due to a higher rate of clinic attendance (and, hence, diagnosis of STDs) among female AI/ANs compared to male AI/ANs. With regard to changes over the 6-year period covered by this report, age-adjusted rates of gonorrhea seem to be steady in both race groups, but age-adjusted rates of Chlamydia seem to be increasing in both races.
This study indicates a 22.8% racial misclassification rate of AI/ANs in the WADOH STD files, which substantially underestimates the true burden of reportable STDs among the Washington AI/AN population. And, the fact that the rate of misclassification seems to be highest among 15-30 year olds will further exacerbate the problem of underestimating the true burden of disease on the very age groups which are at highest risk of contracting STDs.
With the addition of these 738 newly identified AI/AN cases for the years 1995-2000, our study shows a more complete accounting of the magnitude of disparity in the incidence of STDs for AI/ANs in comparison to that for non-AI/ANs. However, now that we have a more accurate idea of the true magnitude and distribution of STDs among AI/ANs in Washington, the challenge is to use these data more effectively in understanding, and ultimately eliminating, these racial disparities. Among the possibilities that need to be explored include whether the AI/AN population does not recognize the problem with STDs in AI/AN communities (perhaps exacerbated by the historical use of State reports that apparently underestimated the disease burden), whether there are historical and/or other factors that increase the tendency of AI/ANs to be risk-takers (and, hence, not protect themselves from STDs), or whether adequate prevention resources are being targeted effectively. In all likelihood, there are probably many factors that contribute to the high STD burden among AI/ANs in Washington, and being racially misclassified in State-based surveillance reports is just one of the problems.
Nonetheless, long-term effects of racial misclassification may include insufficient attention to the high burden of disease from STDs among the AI/AN population. Thus, racial misclassification may lead to poor planning and ineffective implementation of programs, inadequate allocation of funds for prevention efforts among Northwest AI/ANs, and lack of culturally appropriate interventions. Ultimately this may result in a further increase in the burden of disease from STDs among AI/AN communities.
STDs among AI/ANs in Washington Page 10
If racial health disparities are to be addressed, accurate race-specific estimates must be available to monitor trends. The high rates of racial misclassification found in our study document a shortcoming in the identification of race in the Washington STD files. The results of our study will be shared with the managers of the Washington STD program and with tribal communities in the hope that this information will stimulate discussion on how to address this misclassification problem. The results also will be shared with the Northwest tribal health care programs to provide them the accurate data needed to make References funding allocation decisions for their local communities.
1. Centers for Disease Control and Prevention. Sexually Transmitted Disease
Surveillance, 2000. Atlanta, GA: U.S. Department of Health and Human Services,
Centers for Disease Control and Prevention, September 2001.
2. Frost F, Tollestrup K, Ross A, Sabotta E, Kimball E. Correctness of racial coding
of American Indians and Alaska Natives on the Washington State death certificate.
Am J Prev Med. 1994;10:290-294.
3. Frost F, Taylor V, Fries E: Racial misclassification of Native Americans in a
Surveillance, Epidemiology and End Results Registry. Journal of the National
Cancer Institute. 1992, 84, 957-962.
4. Kwong SL, Perkins CI, Snipes KP, Wright WE. Improving American Indian
Cancer data in the California cancer registry by linkage with the Indian Health
Service. J Registry Management. February, 1998:17-20.
5. Becker TM, Bettles J, Lapidus J, Campo J, Johnson CJ, Shipley D, Robertson
LD. Improving cancer incidence estimates for American Indians and Alaska
Natives in the Pacific Northwest. Am J Public Health. 2002 Sep;92(9):1469-71. 6. Sugarman JR, Hill G, Forquera R, Frost FJ. Coding of race on death certificates of
patients of an urban Indian health clinic, Washington, 1973–1988. Provider. 1992
Jul;113–115. 7. Sugarman JR, Holliday M, Ross A, Castorina J, Hui Y. Improving American
Indian cancer data in the Washington State cancer registry Using Linkages with
the Indian Health Service and Tribal Records. Cancer 1996;78(7 Suppl):1564–
8. Sugarman JR, Lawson L. The effect of racial misclassification on estimates of
end-stage renal disease among American Indians and Alaska Natives in the
Pacific Northwest, 1988 through 1990. Am J Kidney Dis. 1993;21:383–386.
9. Sugarman JR, Soderberg R, Gordon J, Rivara FP. Racial misclassification of
American Indians: its effect on injury rates in Oregon, 1989 through 1990. Am J
Public Health. 1993;83:681–684.
10. Stehr-Green PA, Bettles J, Robertson LD. Effect of racial misclassification of
American Indians and Alaskan Natives on Washington State death
certificates,1989–1997. Am J Public Health 2002;92:443-444.