Sample Collection
Speciment Collection, Handling and Preparation
UniCAP/ImmunoCAP assays have been validated for diagnostic use for serum and plasma. Serum and plasma (EDTA-, Heparin- or Citrate-plasma) from venous or capillary blood can be used in all ImmunoCAP instruments and there are no significant differences in results using samples prepared using these different methods (IR 5).
Other body fluids have not been validated but may be used for research purposes.
All samples should be handled as potentially hazardous.
Sodium Azide is routinely used in Phadia controls and may also be used as preservatives in samples, if desired.
No interference from gels in primary sample tubes has been observed.
Plasma vs. serum samples
There are no significant differences in results between plasma and serum samples in ImmunoCAP Specific IgE.
24 samples (1 negative) were tested as serum and as EDTA-, Heparin- and Citrate-plasma.
Each sample was tested in 3 replicates in one assay. The quotient between the results obtained in serum samples and those obtained in the respective type of plasma sample was calculated.
The following mean quotients for the samples were obtained:
| | EDTA-plasma | Heparin-plasma | Citrate-plasma |
| Mean quotient, positive samples | 1,00 | 1,03 | 0,99 |
| The negative serum sample gave a negative result in all types of plasma: |
| | EDTA-plasma | Heparin-plasma | Citrate-plasma |
| Result of negative sample | Negative | Negative | Negative |
Conclusion: There are no significant differences in results between plasma and serum samples in ImmunoCAP Specific IgE.
Interference of icteric, lipemic and hemolytic and samples
Icteric, lipemic or hemolytic samples do not interfere with results in ImmunoCAP Specific IgE (IR 6).
Interference with other Immunoglobulines
No cross-reaction with IgG1, IgG2, IgG3, IgG4, IgA, IgM and IgD in the ImmunoCAP Specific IgE.
Assay was detectable using physiological concentrations of the Immunoglobulins (IR 7 and 8).
Physiological concentrations of Immunoglobulins:
- IgG 8-16 mg/ml
- IgM 0.5-1.9 mg/ml
- IgA 1.4-4,2 mg/ml
- IgD < 0.4 mg/ml
Heat-treatment of patient sera and influence of the IgE test results
When samples are heat-treated, some proteins undergo steric changes that can be irreversible or partly irreversible. Very high temperatures (boiling) can destroy the proteins completely.
It is known that some parts of the IgE molecule (e.g. the receptor binding part) change their conformation during heat-treatment (56° C for 30 minutes).
In ImmunoCAP tests for total IgE (tIgE) and allergen specific IgE (sIgE) stable epitopes of the IgE molecule are used for the anti-IgE antibody conjugate attachment. Mild heat treatment therefore has no influence on the IgE test results.
Stability of IgE antibodies in serum
Samples are stable at +2 - +8 °C for at least a week. Samples can be frozen and thawed at least twice without any effect on results (IR 6) Studies have also shown that IgE antibodies are stable in serum samples after storage at -20º C for years (IR11-13).
This has been verified by testing the same samples in Pharmacia CAP System in 1987,again in ImmunoCAP100 in 1995 and over again in ImmunoCAP 1000 in 2004. The results are shown in Figure 1. This is an example of truly impressive reproducibility over time (IR 11).
Figure 1. Consistency over time. Comparison between results obtained in Pharmacia CAP System™ in 1987, in ImmunoCAP®100 in 1995 and in ImmunoCAP™1000 in 2004.
IR5-8, 11-13 Internal Reference list Doc no 326165