Clinical information
Diagnostic Utility:
- This study investigates the presence of anti-granulocyte autoantibodies.
- It is requested in patients suspected of having autoimmune neutropenia.
- In some patients, the origin of neutropenia is the presence of reactive antibodies against their own granulocytes (autoantibodies).
Method:
Immunofluorescence technique, with flow cytometry reading.
A direct antiglobulin test (DAT) is performed by incubating the patient's leukocytes with different conjugated DATs (Polyspecific, IgG, IgM) labelled with FITC. This test is also called the Direct Test. The presence of IgG and/or IgM class autoantibodies fixed to granulocytes is evidenced by reading the fluorescence intensity (MFI) by flow cytometry.
The study is completed by investigating the presence of free autoantibodies in the patient's serum, performing an indirect DAT, or Indirect Test. The patient's serum (or plasma) is tested against granulocytes from a donor, and after washes, different DATs are added, with the results read by cytometry.
A leukocyte and granulocyte count is performed on the studied sample.
Diagnostic Algorithm:
Results:
The results of autoimmune neutropenia study are:
- Positive Study: anti-granulocyte autoantibodies are detected; results compatible with autoimmune neutropenia (IgG and/or IgM)
- Negative Study: no anti-granulocyte autoantibodies are detected in the study sample
Precautions:
Avoid blood extraction on Fridays or the day before a holiday. The study should ideally be done the day after sample extraction. Granulocyte viability decreases rapidly if more than 24 hours have passed since extraction. When viability is low, the results of the direct test may be inconclusive.
The requested tubes are necessary to obtain a sufficient number of granulocytes from the patient to perform the Direct Test. For paediatric patients, only EDTA tubes should be extracted, with the maximum volume possible based on the child's age.
Response Time:
10 working days
Specimen information
Sample: Peripheral Blood
Tubes in adult patients:
- 4 tubes* of 10 ml of EDTA K3
- 1 tube of 5 ml of EDTA K3
- 1 tube of 5-10 ml without anticoagulant (serum)
* If the patient's degree of neutropenia is known, the volume of blood in EDTA to be extracted can be adjusted. As a guideline, it is recommended:
| Neutrophils x 106/mL | EDTA 10 ml Tubes |
|---|---|
| < 500 | 4 tubes |
| > 500 | 2 tubes |
Tubes in paediatric patients:
- Only EDTA K3 tubes, volume according to the child's age (minimum 5 ml)
Stability:
- At room temperature or at 4°C: 1-2 days
Transport instructions: Preferably at room temperature
Reason for rejection:
- Highly hemolyzed sample
- Samples received in tubes different from those specified in this data sheet.
- If more than 3 days have passed since the extraction, only the Indirect Test is performed.
Administrative information
BST Code: 4812
Test Description: Autoimmune Neutropenia Study
Synonyms: Study of auto-antibodies anti-granulocytes
Section: Immunohematology
BST Rate: Check the updated rates here.
Profiles:
Test 4812 Autoimmune Neutropenia Study is not included in any profile.
References
Xuan Duc Nguyen, Brigitte Flesch, Ulrich J. Sachs, Hartmut Kroll, Harald Klüter, and Michael Müller-Steinhardt. Rapid screening of granulocyte antibodies with a novel assay: flow cytometric granulocyte immunofluorescence test. Transfusion 2009; 49:2700-2708.
Muñiz-Diaz E, Canals C, Montero R et al. Métodos para el diagnóstico de las citopenias inmunes. En: Manual de técnicas de laboratorio en Hematología. Joan Lluis Vives Corrons. 4ª Edición (2014). Elsevier Masson Ed. Barcelona.