Overview: Intron 22 Inversion TestIntroduction: The Intron 22 Inversion Test tests for intron 22 inversion in the F8 gene to diagnose hemophilia A, causing excessive bleeding or bruising, aiding in genetic diagnosis. Affecting 1 in 5,000 males, hemophilia A poses diagnostic challenges due to variable severity. Following 2023 National Hemophilia Foundation (NHF) guidelines, it uses PCR for high accuracy, supporting molecular pathology screening. This test is essential for diagnosis, genetic counseling, and improving outcomes in hematology.
Other Names: F8 Intron 22 Test, Hemophilia A Gene Assay.
FDA Status: Laboratory-developed test (LDT), meeting pathology standards for diagnostic reliability.
Historical Milestone: F8 gene testing began in the 1990s with research by Lakich, who identified the inversion. PCR advancements in the 2000s by Applied Biosystems improved detection, surpassing earlier Southern blot methods.
Purpose: Detects intron 22 inversion to diagnose hemophilia A, guides factor replacement therapy, and evaluates patients with bleeding, aiming to manage disease.
Test Parameters: Intron 22 inversion status
Pretest Condition: No special preparation required. Collect whole blood, buccal swab, or saliva. Report history of bleeding disorders.
Specimen: Whole Blood (EDTA, 3-5 mL), Buccal Swab (sterile swab, 1-2 swabs), Saliva (sterile container, 1-2 mL); 4 mL whole blood in EDTA tube. Transport in a biohazard container.
Sample Stability at Room Temperature: 24 hours
Sample Stability at Refrigeration: 1 week
Sample Stability at Frozen: 1 month
Medical History: Document excessive bleeding or bruising. Include current medications or family history.
Consent: Written consent required, detailing the test's purpose, disease risks (e.g., hemorrhage), and sample collection risks.
Procedural Considerations: Uses PCR to detect inversion, requiring labs with thermal cyclers. Results available in 5-7 days. Performed in labs with strict handling.
Factors Affecting Result Accuracy: Sample degradation or contamination can affect results. Medications may not affect results but require correlation.
Clinical Significance: Positive inversion confirms hemophilia A, guiding therapy. Early management might prevent complications, while untreated cases lead to death. Normal results may require other F8 tests.
Specialist Consultation: Consult a hematologist or genetic counselor for interpretation.
Additional Supporting Tests: Factor VIII levels, PT/PTT, or genetic panel to confirm diagnosis.
Test Limitations: Specific to intron 22; correlation with clinical status needed. False negatives possible with other mutations.
References: NHF Guidelines, 2023; Nature Genetics, Lakich D, 2022.
