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1STT
87857
sensitization and clinical manifestations proceed as follows: eczema and respiratory disease (rhinitis and
bronchospasm) in infants and children less than 5 years due to food sensitivity (milk, egg, soy, and wheat
proteins) followed by respiratory disease (rhinitis and asthma) in older children and adults due to
sensitivity to inhalant allergens (dust mite, mold, and pollen inhalants).
Useful For: Testing for IgE antibodies may be useful to establish the diagnosis of an allergic disease
and to define the allergens responsible for eliciting signs and symptoms. Testing also may be useful to
identify allergens which may be responsible for allergic disease and/or anaphylactic episode, to confirm
sensitization to particular allergens prior to beginning immunotherapy, and to investigate the specificity of
allergic reactions to insect venom allergens, drugs, or chemical allergens.
Interpretation: Detection of IgE antibodies in serum (Class 1 or greater) indicates an increased
likelihood of allergic disease as opposed to other etiologies and defines the allergens that may be
responsible for eliciting signs and symptoms. The level of IgE antibodies in serum varies directly with the
concentration of IgE antibodies expressed as a class score or kU/L.
Reference Values:
Class IgE kU/L Interpretation
0 Negative
1 0.35-0.69 Equivocal
2 0.70-3.49 Positive
3 3.50-17.4 Positive
4 17.5-49.9 Strongly positive
5 50.0-99.9 Strongly positive
6 > or =100 Strongly positive Reference values
apply to all ages.
Clinical References: Homburger HA: Allergic diseases. In Clinical Diagnosis and Management by
Laboratory Methods. 21st edition. Edited by McPherson RA, Pincus MR. WB Saunders, Publ, New York,
Chapter 53, Part VI, pp. 961-971, 2007
First Trimester Maternal Screen
Clinical Information: Multiple marker serum screening has become a standard tool used in obstetric
care to identify pregnancies that may have an increased risk for certain birth defects such as Down
syndrome and trisomy 18. Second-trimester multiple marker screening has been well established for over
a decade. During 2002 through 2006, first-trimester screening has been established as an alternative
option of equal or better performance compared with the best second-trimester screening programs. The
first-trimester screen is performed by measuring analytes in maternal serum that are produced by the fetus
and the placenta. Additionally, the nuchal translucency (NT) measurement is a sonographic marker shown
to be effective in screening fetuses for Down syndrome. A mathematical model is used to calculate a risk
estimate by combining the analyte values, NT measurement, and maternal demographic information. The
laboratory establishes a specific cutoff for each condition, which classifies each screen as either
screen-positive or screen-negative. A screen-positive result indicates that the value obtained exceeds the
established cutoff. A positive screen does not provide a diagnosis, but indicates that further evaluation
should be considered. Serum Analytes Human chorionic gonadotropin (total beta-hCG): hCG is a
glycoprotein consisting of alpha and beta subunits. hCG is synthesized by placental cells starting very
early in pregnancy and serves to maintain the corpus luteum and, hence, progesterone production during
the first trimester. Thereafter, the concentration of hCG begins to fall as the placenta begins to produce
steroid hormones and the role of the corpus luteum in maintaining pregnancy diminishes. Increased total
hCG levels are associated with an increased risk for Down syndrome. Pregnancy-associated plasma
protein A (PAPP-A): PAPP-A is a 187 kDA protein comprised of 4 subunits: 2 PAPP-A subunits and 2
pro-major basic protein (proMBP) subunits. PAPP-A is a metalloproteinase that cleaves insulin-like
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