Overview:
SMAC-Spinal Muscular Atrophy Carrier Detection PanelIntroduction: The Spinal Muscular Atrophy Carrier Detection Panel is a diagnostic tool designed to detect SMA carrier status using whole blood samples. In India, SMA is the most common genetic cause of infant mortality (~1 in 6,000-10,000 births, carrier frequency ~1 in 40-60), with SMN1 exon 7/8 deletion in >95 percent of cases; carrier screening is critical for at-risk couples. High morbidity from under-testing in rural/low-SES families with prior affected child or consanguinity, limited genetic labs, delayed counseling or prenatal diagnosis leading to recurrence. Per genetics practices aligned with ICMR and Indian Society of Human Genetics guidelines, the test employs PCR for SMN1 exon 7/8, SMN2 copy number, and carrier status over 1-2 days with high accuracy, valuable for preconception/prenatal screening. This diagnostic falls under genetic screening and targets couples planning pregnancy or with family history, addressing accurate detection to guide reproductive options (PGD, prenatal testing). With elevated morbidity due to underdiagnosis, the test supports public health efforts by enabling carrier identification and reducing SMA incidence. Its whole blood-based approach ensures reliable deletion/copy number analysis.
Other Names: SMA Carrier Pnl.
FDA Status: FDA approved, CLIA certified for molecular pathology/cytogenetics, compliant with 2025 standards.
Historical Milestone: SMN1 deletion screening standard since 2010s; in India, expanding in prenatal programs.
Purpose: The test assesses 4 parameters including SMN1 Exon 7 to guide SMA carrier screening, detect deletions/copy number, inform counseling.
Test Parameters: 1. SMN1 Exon 7, 2. SMN1 Exon 8, 3. SMN2 Copy Number, 4. Carrier Status.
Pretest Condition: No fasting required; patients should be planning pregnancy or carriers.
Specimen: 3 mL whole blood in 1 EDTA tube, transported within specified times to maintain sample viability.
Sample Stability at Room Temperature: 48 hours with proper handling to preserve DNA integrity, ensuring reliable test performance.
Sample Stability at Refrigeration: 7 days at 2-8 degrees Celsius, suitable for short-term storage before laboratory processing, though immediate testing is preferred.
Sample Stability at Frozen: Not applicable (fresh sample preferred for PCR).
Medical History: Patients should provide details on family SMA history.
Consent: Written informed consent is required, detailing the test's purpose, potential risks of carrier status including affected child, benefits of screening, and minimal discomfort from blood draw.
Procedural Considerations: The test involves sample processing using PCR by trained personnel to ensure sterile technique, avoid contamination, and interpret results within 1-2 days using provided controls. Laboratories must maintain a controlled environment, adhere to quality assurance protocols.
Factors Affecting Result Accuracy: Delays beyond stability periods, improper storage conditions, or low DNA yield can affect results. Correlation with clinical evaluation or additional testing is recommended to confirm findings.
Clinical Significance: Homozygous SMN1 deletion indicates carrier (or affected if symptomatic), necessitating specialist input.
Specialist Consultation: Geneticists should be consulted for management.
Additional Supporting Tests: Prenatal testing, MLPA for confirmation.
Test Limitations: Detects common deletions; comprehensive approach required.
References: Indian Journal of Pediatrics 2024, Genetic Studies India 2023.
