A Novel Targeted Screening Tool for Hypogammaglobulinemia: Measurement of Serum Immunoglobulin (IgG, IgM, IgA) Levels from Dried Blood Spots (Ig-DBS Assay).
OBJECTIVE
To develop an assay to quantify serum immunoglobulin (IgG, IgM, IgA) levels using dried blood spots (DBS) obtained on collection cards to be used as a tool for targeted screening for hypogammaglobulinemia.


METHODS
DBS samples, along with simultaneous serum samples, were collected from 107 healthy individuals (11 months to 57 years of age). After eluting proteins from DBS, IgG, IgM, and IgA were quantified by an enzyme-linked immunosorbent assay (ELISA). The Ig-DBS assay was validated through calibration curve performance, intra- and inter-assay precision, accuracy, specificity, selectivity, and linearity. The ELISA measurements were compared with serum Ig levels obtained using a standard nephelometry assay on serum samples collected simultaneously with the DBS samples and the results of the two assays were correlated. The stability of IgG, IgM, and IgA in the DBS was tested at room temperature, 36° to 38 °C, 2 to 8 °C, and -25 to -40 °C, from 4 to 14 days.


RESULTS
The Ig-DBS assay demonstrated precision, accuracy, specificity, selectivity, and linearity. Using the identified correlation coefficients of 0.834 for IgG, 0.789 for IgM, and 0.918 for IgA, the standard nephelometry-based normal reference ranges for all 3 serum Ig isotypes could be used with the Ig-DBS assay in individuals ≥16 years of age. The DBS samples were stable for 14 days at room temperature in a closed polyethylene bag.


CONCLUSIONS
The Ig-DBS assay is both sensitive and accurate for quantification of serum immunoglobulins. Samples are sufficiently stable at ambient temperature to allow for convenient shipping and analysis at a centralized laboratory. This assay therefore presents a new option for screening patients ≥16 years of age for hypogammaglobulinemia in any setting.
Baxalta US, Inc., Global Clinical Research, One Baxter Way, Westlake Village, CA, 91362, USA. leman.yel@baxalta.com.|University of California, Irvine, CA, USA. leman.yel@baxalta.com.
Leman
L
Yel
Baxalta US, Inc., North American Medical Affairs, Bannockburn, IL, USA.
Christopher J
CJ
Rabbat
Mount Sinai School of Medicine, New York, NY, USA.
Charlotte
C
Cunningham-Rundles
Texas Children's Hospital, Baylor College of Medicine, Houston, TX, USA.
Jordan S
JS
Orange
University of Washington and Seattle Children's Hospital, Seattle Children's Research Institute, Seattle, WA, USA.
Troy R
TR
Torgerson
Medical College of Wisconsin, Milwaukee, WI, USA.
James W
JW
Verbsky
Baxalta US, Inc., Global Quality, Westlake Village, CA, USA.
Yeong
Y
Wang
Quest Diagnostics, Valencia, CA, USA.
Maoyong
M
Fu
Quest Diagnostics, Valencia, CA, USA.
Terry S
TS
Robins
Quest Diagnostics, Valencia, CA, USA.
Marc S
MS
Edwards
Quest Diagnostics, Valencia, CA, USA.
Jesper
J
Nymann-Andersen
D000293:Adolescent; D000328:Adult; D000361:Agammaglobulinemia / Q000175:diagnosis*; D002648:Child; D002675:Child, Preschool; D059788:Dried Blood Spot Testing / Q000379:methods*; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D007070:Immunoglobulin A / Q000097:blood; D007074:Immunoglobulin G / Q000097:blood; D007075:Immunoglobulin M / Q000097:blood; D007223:Infant; D008403:Mass Screening / Q000379:methods*; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D055815:Young Adult
D007070:Immunoglobulin A; D007074:Immunoglobulin G; D007075:Immunoglobulin M
DBS; ELISA; Ig-DBS assay; dried blood spots; immunoglobulin; nephelometry; primary immunodeficiency; validation