Effect of specimen storage conditions on newborn dried blood spots used to assess Toxoplasma gondii immunoglobulin M (IgM).
BACKGROUND
Newborn screening programs store-under varying conditions-residual dried blood spots (DBS). Residual DBS were used to investigate the contribution of congenital infection with Toxoplasma gondii to the etiology of hydrocephalus and as a key step, we assessed the effect of storage conditions on the stability of newborn screening biomarkers.


METHODS
Infants with hydrocephalus (410 cases) were identified using population-based birth defects surveillance systems in California, North Carolina, and Texas. Infants without birth defects (448 controls) were randomly selected from the same geographic areas and time periods. California stores DBS with controlled temperature, while North Carolina and Texas store DBS under ambient conditions. After removal of personal identifiers, DBS were tested for Toxo-specific immunoglobulin-M (Toxo-IgM). Because of poor elution of DBS stored in ambient conditions, additional biomarkers were tested on a specimen subset.


RESULTS
Among 858 DBS tested, Toxo-IgM was found in 3 cases and no controls from California (N=515) and in no specimens from North Carolina or Texas (N=343). Among the 98 specimens tested for selected biomarkers, statistically significant differences were found for California vs. combined North Carolina and Texas DBS (thyroid stimulating hormone, phenylalanine, methionine, leucine and citrulline p<0.0001; tyrosine and valine p<0.001).


CONCLUSIONS
Storage conditions for residual DBS had an effect on the ability to extract, recover, and accurately measure Toxo-IgM and other biomarkers from the filter paper matrix.
Centers for Disease Control and Prevention, Atlanta, GA, United States. jmei@cdc.gov
Joanne V
JV
Mei
LiXia
L
Li
Sonja A
SA
Rasmussen
Sarah
S
Collier
Jaime L
JL
Frias
Margaret A
MA
Honein
Gary M
GM
Shaw
Fred
F
Lorey
Robert
R
Meyer
Shu
S
Chaing
Mark A
MA
Canfield
Jeffrey
J
Jones
W Harry
WH
Hannon
D000818:Animals; D001774:Blood Chemical Analysis / Q000379:methods*; D001800:Blood Specimen Collection / Q000379:methods*; D006801:Humans; D006849:Hydrocephalus / Q000097:blood / Q000276:immunology / Q000469:parasitology; D007075:Immunoglobulin M / Q000097:blood*; D007231:Infant, Newborn; D012680:Sensitivity and Specificity; D014122:Toxoplasma / Q000276:immunology* / Q000302:isolation & purification*
D007075:Immunoglobulin M