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Cytogenetic guidelines for fragile X studies tested in routine practice
G W Dewald1, D D Buckley, J L Spurbeck
1Cytogenetics Laboratory, Mayo Clinic, Rochester, Minnesota 55905.
American Journal of Medical Genetics
|December 1, 1992
Summary
This study evaluated fragile X (fra(X)) testing guidelines by analyzing 1,033 patient specimens. Results show fra(X) was detected in 3.7% of cases, highlighting the need for standardized fra(X) analysis protocols.
Area of Science:
- Genetics
- Cytogenetics
- Molecular Biology
Background:
- Established guidelines exist for fragile X (fra(X)) testing in peripheral blood lymphocytes.
- Evaluating the efficacy and reliability of these proposed guidelines is crucial for accurate diagnosis.
Purpose of the Study:
- To assess the validity of current fra(X) study guidelines using a large cohort of patient specimens.
- To determine the prevalence of fra(X) in a diverse patient population and identify factors influencing detection rates.
Main Methods:
- Reviewed 1,033 consecutive specimens referred for fra(X) analysis.
- Cultured cells using standard media (Medium 199, RPMI 1640) with fra(X) induction agents (5-fluorodeoxyuridine, excess thymidine).
- Performed karyotyping and fra(X) expression analysis on banded cells (20–130 cells per specimen).
Main Results:
- Fragile X (fra(X)) positive cells (≥4%) were identified in 3.7% of cases (38/1,033), including 3.9% of males and 2.7% of females.
- An additional 4 females presented with 1–3% fra(X) cells.
- Detection rates varied based on the stress system used, with some cases positive in only one system.
- Chromosome breakage and fra(3)(p14) were found to be unreliable quality control indicators for fra(X) stress systems.
Conclusions:
- The study provides empirical data to evaluate existing fra(X) testing guidelines.
- A significant percentage of fra(X) cases require extensive cell screening for accurate detection.
- Current quality control indicators for fra(X) stress systems may not be reliable.