Emerg Infect DisEIDEmerging Infectious Diseases1080-60401080-6059Centers for Disease Control and Prevention272597906-135510.3201/eid1304.061355Letters to the EditorToxoplasma gondii Prevalence, United StatesToxoplasma gondii Prevalence, United StatesJonesJeffrey L.*Kruszon-MoranDeanna†WilsonMarianna*Centers for Disease Control and Prevention, Atlanta, Georgia, USACenters for Disease Control and Prevention, Hyattsville, Maryland, USAAddress for correspondence: Jeffrey L. Jones, Centers for Disease Control and Prevention, Mailstop F22, 4770 Buford Highway, Atlanta, GA 30341, USA; email: JLJones@cdc.gov42007134656657JonesJL, Kruszon-MoranDK, WilsonM. Toxoplasma gondii infection in the United States, 1999–2000.Emerg Infect Dis. 2003;9:1371–4.14718078Keywords: Toxoplasmatoxoplasmosisprevalenceserologyletter
To the Editor: We correct the prevalence of Toxoplasma gondii immunoglobulin (Ig) G antibodies published in Emerging Infectious Diseases in 2003 (1). An incorrect cutoff value in the computer program used to calculate seropositivity of anti–T. gondii IgG antibody resulted in some incorrect prevalence rates. We discovered this error when analyzing more recent National Health and Nutrition Examination Survey (NHANES) data.
The cutoff value for anti–T. gondii IgG seropositivity used in the prior publication (1) was >6 IU, which is the correct value for NHANES III 1988–1994 data (2) but not for NHANES 1999–2000 data. Because of a change by the T. gondii test kit manufacturer, the cutoff value for NHANES 1999–2000 seropositivity data was increased to ≥10 IU. This cutoff change from >6 to ≥10 IU does not cause a large difference in the T. gondii seroprevalence reported. In addition, it does not change the overall findings of the article or the overall relationship between NHANES III (1988–1994) and NHANES 1999–2000. However, it does produce a borderline change for 2 demographic subgroups (non-Hispanic white persons and persons born in the United States), for whom the difference from NHANES III to NHANES 1999–2000 data reached statistical significance at p<0.05 in the t test, but the 95% confidence intervals (CIs) for the prevalence estimates for these groups still overlapped between NHANES III and NHANES 1999–2000 (i.e., the t test is a less conservative measure of association than CI).
After this correction, the overall T. gondii antibody prevalence according to NHANES 1999–2000 data changed from 15.8% (95% CI 13.5%–18.1%) to 14.3% (95% CI 12.3%–16.2%). The Table shows the overall and stratified seroprevalence rates for NHANES 1999–2000 (corrected) compared with NHANES III (no corrections needed).
1Comparison of<italic>Toxoplasma gondii</italic> IgG antibody seroprevalence, NHANES 1999–2000 and NHANES III (1988–1994)*†
NHANES 1999–2000
NHANES III (1988–1994)
N‡
Prevalence
95% CI
N‡
Prevalence
95% CI
Total
4,234
14.3
12.3–16.2
11,132
16.0
14.5–17.5
Sex
Male
2,013
15.2
12.4–18.0
5,144
16.7
14.8–18.6
Female
2,221
13.4
11.2–15.5
5,988
15.3
13.5–17.0
Race/ethnicity
Non-Hispanic white
1,293
10.8
8.1–13.6
3,304
14.3
12.5–16.2
Non-Hispanic black
1,027
16.8
13.4–20.3
3,674
18.0
16.1–19.8
Mexican American
1,553
14.2
10.1–18.4
3,661
18.3
16.7–20.0
Age group, y
12–19
2,105
7.3
4.7–10.0
2,749
8.5
6.4–10.5
20–29
735
11.9
9.5–14.4
3,100
15.2
12.1–18.3
30–39
726
17.0
12.9–21.2
2,960
16.1
14.6–17.6
40–49
668
18.7
15.0–22.3
2,323
22.2
19.4–25.0
Country of birth
United States
3,211
10.5
8.3–12.8
8,606
14.1
12.7–15.5
Not United States
995
32.0
24.0–39.9
2,493
27.9
24.1–31.7
*IgG, immunoglobulin G; NHANES, National Health and Examination Survey; CI, confidence interval. †Sex, race/ethnicity, and total values are age-adjusted to the 2000 census–estimated population using the 4 age categories shown. ‡Totals for the race/ethnicity and country-of-birth categories do not add up to the total number because of an “other” category (not shown) or because persons did not provide a response to country-of-birth questions.
Suggested citation for this article: Jones JL, Kruszon-Moran D, Wilson M. Toxoplasma gondii prevalence, United States [letter]. Emerg Infect Dis [serial on the Internet]. 2007 Apr [date cited]. Available from http://www.cdc.gov/eid/content/13/4/656.htm
ReferencesJonesJL, Kruszon-MoranDK, WilsonMToxoplasma gondii infection in the United States, 1999–2000.Emerg Infect Dis2003;9:1371–414718078JonesJL, Kruszon-MoranDK, WilsonM, McQuillanG, NavinT, McAuleyJBToxoplasma gondii infection in the United States: seroprevalence and risk factors.Am J Epidemiol2001;154:357–6510.1093/aje/154.4.35711495859