Purpose of the Study
Sudden infant death syndrome (SIDS) remains a diagnosis of exclusion with few clues as to its cause. Previous evaluations regarding anaphylaxis and SIDS are few and limited. The purpose of this study is to analyze forensic blood samples for evidence of anaphylaxis in children dying of SIDS against age-matched controls who died from defined nonanaphylactic causes.
21 infants (13 males and 8 females) who died from SIDS were selected from a population of deaths investigated by the Bexar County Medical Examiner's Office between 1990 and 1995. Thirteen age-matched controls (9 males and 4 females) were identified who died from defined, nonanaphylactic causes.
Frozen forensic blood specimens from these subjects were evaluated for the following: 1) total immunoglobulin E (IgE) (IU/mL); 2) latex, cat, dust mite, milk, soy, wheat, peanut, egg, and tomato specific-IgE radioallergosorbent (RAST) testing; and 3) serum tryptase levels (U/L). RAST test results were considered positive and potentially significant at measured counts >500.
The 21 SIDS cases (median age, 3 months) and the 13 control cases (median age, 4 months) demonstrated similar total IgE levels of 9.8 ± 1.1 IU/mL and 19.9 ± 2.8 IU/mL, respectively, (P = .59). The frequency of detectable (0.5 U/L) serum tryptase levels among SIDS cases (10/51) were similar to controls ((3/13), P = .72). The frequency of positive RAST tests was 39% (20/51) in SIDS and 38% (5/13) in controls (P= .99). Differences in frequencies of positive RAST tests in SIDS and control cases were not statistically significant for any allergen that was tested. The most frequently detected allergen-specific IgE was to milk and was similar in the SIDS (22%) subjects and the controls (31%, P = .48).
Elevated tryptase levels and allergen-specific IgE (milk, soy, wheat, peanuts, egg, tomato, dust mites, cat, and latex) were demonstrated in some of the infants who died from SIDS but were no more common than age-matched controls. It is therefore unlikely that anaphylaxis is a common cause in SIDS.
There has been much study and debate over possible causes for the tragedy of SIDS. The anaphylaxis hypothesis has been put forth in several studies but never substantiated. This study relates that allergen hypersensitivity and anaphylaxis is unlikely to be a factor in this entitity. However, one must realize that total and specific IgE levels in infants are usually low compared with adults, and reference values for infant RAST interpretations are not standardized. Furthermore, tryptase often can be undetectable in cases of anaphylaxis and is not a definitive diagnostic tool. Nevertheless, this is a nice analysis of an important question. The authors propose that further study is required and desirable.