Correspondence

Screening for Neonatal Toxoplasmosis

N Engl J Med 1994; 331:1458-1459November 24, 1994

Article

To the Editor:

Guerina et al. (June 30 issue)1 claim a “favorable” cost-benefit ratio for neonatal screening for congenital toxoplasmosis, but their data are inadequate. Although they mention laboratory and personnel costs, they do not include the added costs of confirming the diagnosis, reporting and treating the disease, counseling families, training clinical personnel, and tracking cases. Moreover, the data presented are not sufficient to determine whether there are any savings in either medical costs or lifetime social costs.

In the study by Guerina et al., the incidence of congenital toxoplasmosis in Massachusetts and New Hampshire was 10 times lower than predicted. The incidence in other parts of the United States, particularly the West, may be even lower. Multiple treatment regimens were given, with no untreated control groups. For the affected patients, outcomes ranged from normal development to substantial neurologic impairment. Furthermore, because the infection occurred in utero, it was impossible to determine how much of the observed damage was due to prenatal disease.

In a pilot program to test for prenatal toxoplasmosis with commercial kits, retesting by a reference laboratory showed a false positive rate of 29 percent. False positive tests cause maternal anxiety and risky, inappropriate treatment. Guerina et al. treated two infants with positive tests but no evidence of disease solely because of the physician's “preferences.”

Our program cost $35 per patient, including confirmation of results and counseling of patients, but not including treatment and follow-up. We discontinued our study because of high costs and low prevalence of disease.

A complete program to manage congenital toxoplasmosis must include the prenatal testing and treatment of infected mothers. However, unlike infection with the human immunodeficiency virus, congenital toxoplasmosis has not been shown to pose a severe enough threat to warrant such a complex, expensive program. The incomplete approach and limited cost data provided by Guerina et al. offer no convincing evidence that neonatal screening for congenital toxoplasmosis is a health care priority.

Edgar J. Schoen, M.D.
Steven Black, M.D.
Dena Cohen, R.N., M.P.H.
Kaiser Permanente Medical Center, Oakland, CA 94611-5693

1 References

1. 1

   Guerina NG, Hsu H-W, Meissner HC, et al. Neonatal serologic screening and early treatment for congenital Toxoplasma gondii infection. N Engl J Med 1994;330:1858-1863
   Full Text | Web of Science | Medline

To the Editor:

The report by Guerina et al. underestimates the incidence of congenital toxoplasmosis in the United States. The authors do not elaborate on the drawback of testing newborns for IgM antibodies: the immature immune system of the fetus frequently fails to mount an antibody response to toxoplasma antigens. The IgM assay used by the authors has a reported sensitivity of 72.7 percent.1 We found that only 2 of 12 congenitally infected newborns had IgM responses with the sensitive Western blot assay.2 In the study by Guerina et al., three of the five infants with clinically diagnosed infection had negative IgM filter-paper tests, and two had negative results in a confirmatory assay. One could argue that the IgM response had already waned, but still neonatal screening would have missed a proportion of positive cases. Thus, we believe that maternal screening would give a better estimate of the true incidence of congenital toxoplasmosis.

Israel Potasman, M.D.
Neora Pick, M.D.
Isaac Srugo, M.D.
Bnai Zion Medical Center, Haifa, Israel 31048

2 References

1. 1

   Naot Y, Desmonts G, Remington JS. IgM enzyme-linked immunosorbent assay test for the diagnosis of congenital Toxoplasma infection. J Pediatr 1981;98:32-36
   CrossRef | Web of Science | Medline

2. 2

   Potasman I, Araujo FG, Thulliez P, Desmonts G, Remington JS. Toxoplasma gondii antigens recognized by sequential samples of serum obtained from congenitally infected infants. J Clin Microbiol 1987;25:1926-1931
   Web of Science | Medline