There are two reasons to test for proteins or protein allergens:
To determine whether a user or patient is allergic to latex gloves. These tests are covered in the article ____ by ____ in this supplement.
To determine whether a particular glove or brand of gloves is likely to cause sensitisation of non-allergic individuals or an allergic reaction in previously sensitised individuals.
Users and purchasers of gloves should have two aims in mind when considering the protein allergen issue:
To reduce the numbers of individuals sensitised to latex proteins,
To avoid eliciting allergic reactions in individuals already sensitised to latex proteins. Previously sensitised individuals can have an allergic reaction provoked by much lower levels of protein than is required to sensitise in the first place.
Table 3 details the advantages and disadvantages of each test.
| Test | Advantages | Disadvantages |
|---|---|---|
| Skin Prick Test (SPT) | Specific for allergens. Very sensitive. The "ultimate" proof of allergic reactions in-vivo. Good correlation with RI and EI methods. | Requires NRL sensitised individuals who are willing to be tested, therefore not acceptable for routine use. It is dependent on the subject having been sensitised to the allergens in the latex and on the degree of sensitivity of the individual. |
| Total Extractable Protein (TEP) | Correlation with SPT quite good. Reproducible. Stable reagents and colour. Relatively easy to perform. | Non-specific - detects all proteins, not just allergens. Comparatively insensitive c.f. immunoassay methods. Susceptible to interfering substances - for example, surfactants can produce lower than expected readings while accelerators can produce higher readings. |
| RAST Inhibition (RI) | Sensitive, reproducible and specific - only measures allergens. Readily available (widespread). In-vitro compared with SPT which is in-vivo. | Depends on pooled human sera for the antibodies. Time consuming and expensive. Pooled sera must include all relevant antibodies. Requires handling of radioactive reagents. Less sensitive than the SPT - generally accepted to detect only 50-60% of latex sensitive subjects (but claims have been made for up to 94% sensitivity with some recent assays) Citation:Keith Amsterdam Conference 1996 occupational health |
| ELISA Inhibition (EI) | Good correlation with SPT and RI. Simple No radioactive reagents required. Automation possible, therefore relatively cheap. Readily available (widespread technique). In-vitro c.f. in-vivo SPT. | Depends on pooled human sera for the antibodies (as with RI). Pooled sera must include all relevant antibodies. Difficult to standardise. Less sensitive than the SPT - generally accepted to detect only 50-60% of latex sensitive subjects. |
| LEAP | Very sensitive c.f. TEP. Less susceptible to interfering substances c.f. TEP. Specific for latex proteins. | Measures antigens not allergens, therefore is a form of TEP. Difficult to standardise. Reproducibility unclear. |
| Immunoblotting | Useful R&D technique. | Qualitative (not quantitative). Insensitive to small molecular weight peptides. |
| Immunospot | Simple | Semi-quantitative only. Relatively insensitive. Time consuming. Difficult to standardise. |
| Electrophoretic Methods (e.g., RIE/RRIE & CIE/CRIE) | Differentiates between antigens and allergens. Useful research tool. | Requires rabbit serum with relevant antibodies. Time consuming. Research purposes only. |