Laboratory Testing for ALPS Diagnosis

Required Laboratory Tests

The American Society of Hematology recommends that for diagnosing ALPS, flow cytometry must be used to measure TCRαβ+ CD3+ CD4-CD8- double-negative T cells (DNTs), which must be ≥1.5% of total lymphocytes or ≥2.5% of CD3+ T cells in the setting of normal or elevated lymphocyte counts 1, 2
DNT levels >3% of total lymphocytes (or >5% of T lymphocytes) are essentially pathognomonic for ALPS, according to the National Institutes of Health 1, 2
The flow cytometry panel must distinguish from TCRγδ+ DNTs by costaining with TCR-directed antibodies, as recommended by the American College of Medical Genetics 1, 2

The diagnostic algorithm for ALPS involves screening with DNT percentage by flow cytometry in any patient with chronic (>6 months) lymphadenopathy and/or splenomegaly plus autoimmune features, as suggested by the European Society for Immunodeficiencies 1
If DNTs ≥1.5% of total lymphocytes, proceed to primary accessory testing (apoptosis assay and/or genetic testing) for definitive diagnosis, according to the American Academy of Allergy, Asthma, and Immunology 1

The American Society of Hematology advises against screening for ALPS based solely on DNT levels between 1.0-1.5%, as these can occur in healthy individuals or reactive conditions like systemic lupus erythematosus 1, 2
The National Institutes of Health recommends not relying on apoptosis testing alone for patients with suspected somatic FAS or FASLG mutations, as these may show normal results 1, 2
Ensure lymphocyte counts are normal or elevated when interpreting DNT percentages; lymphopenia invalidates the DNT criterion, as stated by the American College of Medical Genetics 1, 2

The National Institutes of Health recommends the revised diagnostic criteria for Autoimmune Lymphoproliferative Syndrome (ALPS), which includes required criteria such as chronic nonmalignant, noninfectious lymphadenopathy or splenomegaly, and elevated CD3+TCRαβ+ CD4-CD8- double-negative T cells, with normal or elevated lymphocyte counts 3, 4, 5
The National Institutes of Health suggests that primary accessory criteria, such as defective lymphocyte apoptosis or somatic or germline pathogenic mutation in FAS, FASLG, or CASP10, are needed for a definitive diagnosis of ALPS 6, 3, 5
The National Institutes of Health proposes that secondary accessory criteria, including elevated biomarkers, typical immunohistological findings, autoimmune cytopenias, or compatible family history, can support a probable diagnosis of ALPS 3, 5, 7

The misuse of the term "Benson and Alpen criteria" may indicate a miscommunication or confusion with ALPS diagnostic criteria, highlighting the need for clarification of the specific clinical context 6