Quantitative serum immunoglobulin tests.

What is the test? Immunoglobulins are protein molecules. They contain antibody activity and are produced by the terminal cells of B-cell differentiation known as 'plasma cells'. There are five classes of immunoglobulin (Ig): IgG, IgM, IgA, IgD and IgE. In normal serum, about 80% is IgG, 15% is IgA, 5% is IgM, 0.2% is IgD and a trace is IgE. Quantitative serum immunoglobulin tests are used to detect abnormal levels of the three major classes (IgG, IgA and IgM). Testing is used to help diagnose various conditions and diseases that affect the levels of one or more of these immunoglobulin classes. Some conditions cause excess levels, some cause deficiencies, and others cause a combination of increased and decreased levels. IgD and IgE will not be discussed in this article.

Antinuclear antibody test.

The antinuclear antibody (ANA) test is widely used as a serological marker of autoimmune disease. Antinuclear antibodies are immunoglobulins or antibodies that bind to one or more antigens expressed within the nucleus of human cells. Used selectively, the ANA test can be a useful laboratory tool to help confirm or exclude the diagnosis of systemic rheumatic disease. However, the relatively high prevalence of ANAs in other inflammatory conditions, as well as healthy individuals, can make a positive result difficult to interpret.

An Australian Consensus on Infant Feeding Guidelines to Prevent Food Allergy: Outcomes From the Australian Infant Feeding Summit.

BACKGROUND: Infant feeding in the first postnatal year of life has an important role in an infant's risk of developing food allergy. Consumer infant feeding advice is diverse and lacks consistency. AIM: The Australian Infant Feeding Summit was held with the aim of achieving national consensus on the wording of guidelines for infant feeding and allergy prevention. METHODS: Two meetings were hosted by the Centre for Food and Allergy Research, the Australasian Society of Clinical Immunology and Allergy, and the Australian National Allergy Strategy. The first meeting of 30 allergy researchers, clinicians, and consumers assessed the evidence. The second consensus meeting involved 46 expert stakeholders including state and federal health care agencies, consumers, and experts in allergy, infant feeding, and population health. RESULTS: Partner stakeholders agreed on consensus wording for infant feeding advice: CONCLUSIONS: Consensus was achieved in a context in which there is a high prevalence of food allergy. Guidelines for other countries are being updated. Provision of consistent wording related to infant feeding to reduce food allergy risk will ensure clear consumer advice.

Skin prick testing predicts peanut challenge outcome in previously allergic or sensitized children with low serum peanut-specific IgE antibody concentration.

Peanut allergy is transient in some children but it is not clear whether quantitating peanut-specific IgE by Skin Prick Test (SPT) adds additional information to fluorescent-enzyme immunoassay (FEIA) in discriminating between allergic and tolerant children. To investigate whether SPT with a commercial extract or fresh foods adds additional predictive information for peanut challenge in children with a low FEIA (<10 k UA/L) who were previously sensitized, or allergic to peanuts. Children from a hospital-based allergy service who were previously sensitized or allergic to peanuts were invited to undergo a peanut challenge unless they had a serum peanut-specific IgE>10 k UA/L, a previous severe reaction, or a recent reaction to peanuts (within two years). SPT with a commercial extract, raw and roasted saline soaked peanuts was performed immediately prior to open challenge in hospital with increasing quantity of peanuts until total of 26.7 g of peanut was consumed. A positive challenge consisted of an objective IgE mediated reaction occurring during the observation period. 54 children (median age of 6.3 years) were admitted for a challenge. Nineteen challenges were positive, 27 negative, five were indeterminate and three did not proceed after SPT. Commercial and fresh food extracts provided similar diagnostic information. A wheal diameter of >or=7 mm of the commercial extract predicted an allergic outcome with specificity 97%, positive predictive value 93% and sensitivity 83%. There was a tendency for an increase in SPT wheal since initial diagnosis in children who remained allergic to peanuts while it decreased in those with a negative challenge. The outcome of a peanut challenge in peanut sensitized or previously allergic children with a low FEIA can be predicted by SPT. In this cohort, not challenging children with a SPT wheal of >or=7 mm would have avoided 15 of 18 positive challenges and denied a challenge to one out of 27 tolerant children.