title: The limitations of qPCR telomere length measurement in diagnosing dyskeratosis congenita.
abstract: BACKGROUND
  Telomere length <1st percentile-for-age in leukocyte subsets by flow cytometry with fluorescence in situ hybridization (flow FISH) is highly sensitive and specific in diagnosing patients with dyskeratosis congenita (DC), a telomere biology disorder.
  
  
  METHODS
  We evaluated the clinical utility of the high-throughput quantitative real-time PCR (qPCR) relative telomere length (RTL) measurement as a diagnostic test for DC in patients with a priori clinical and/or genetic DC diagnoses. We calculated the sensitivity and specificity of RTL at different age-specific percentile cutoffs in 31 patients with DC and 51 mutation-negative relatives, and evaluated RTL difference by disease genotype.
  
  
  RESULTS
  qPCR RTL <1st percentile-for-age failed to identify more than 60% of the patients already known to have DC (sensitivity = 39%, specificity = 98%). Three-quarters of DC patients had RTL below the 10th percentile-for-age (sensitivity = 74%), as did 12% of the unaffected relatives (specificity = 88%).
  
  
  CONCLUSIONS
  Our findings suggest that the qPCR RTL method is not optimal for diagnosing DC. In light of these limitations, leukocyte flow FISH telomere length remains the recommended molecular test for diagnosing DC.
authors.affiliation: Clinical Genetics Branch Division of Cancer Epidemiology and Genetics National Cancer Institute, National Institutes of Health 9609 Medical Center Drive Rockville Maryland 20850.
authors.forename: Shahinaz M
authors.initials: SM
authors.lastname: Gadalla
authors.affiliation: Clinical Genetics Branch Division of Cancer Epidemiology and Genetics National Cancer Institute, National Institutes of Health 9609 Medical Center Drive Rockville Maryland 20850.
authors.forename: Payal P
authors.initials: PP
authors.lastname: Khincha
authors.affiliation: Biostatistics Branch Division of Cancer Epidemiology and Genetics National Cancer Institute National Institute of Health 9609 Medical Center Drive Rockville Maryland 20850.
authors.forename: Hormuzd A
authors.initials: HA
authors.lastname: Katki
authors.affiliation: Clinical Genetics Branch Division of Cancer Epidemiology and Genetics National Cancer Institute, National Institutes of Health 9609 Medical Center Drive Rockville Maryland 20850.
authors.forename: Neelam
authors.initials: N
authors.lastname: Giri
authors.affiliation: Occupational and Environmental Epidemiology Branch Division of Cancer Epidemiology and Genetics National Cancer Institute National Institutes of Health 9609 Medical Center Drive Rockville Maryland 20850.
authors.forename: Jason Y Y
authors.initials: JY
authors.lastname: Wong
authors.affiliation: Center for International Blood and Marrow Transplant Research 500 5th St N Minneapolis Maryland 55401.
authors.forename: Stephen
authors.initials: S
authors.lastname: Spellman
authors.affiliation: Section on Growth and Obesity Division of Translational Medicine Eunice Kennedy Shriver National Institute of Child Health and Human Development National Institutes of Health 10 Center Drive, Building 10-CRC Bethesda Maryland 20892.
authors.forename: Jack A
authors.initials: JA
authors.lastname: Yanovski
authors.affiliation: Departments of Pediatrics and Physiology University of Tennessee Health Science Center and Children's Foundation Research Institute Le Bonheur Children's Hospital 50 North Dunlap Street, Room 454R Memphis Tennessee 38103.
authors.forename: Joan C
authors.initials: JC
authors.lastname: Han
authors.affiliation: Channing Division of Network MedicineDepartment of MedicineBrigham and Women's Hospital and Harvard Medical SchoolBostonMassachusetts02115; Program in Genetic Epidemiology and Statistical GeneticsHarvard School of Public HealthBostonMassachusetts02115.
authors.forename: Immaculata
authors.initials: I
authors.lastname: De Vivo
authors.affiliation: Clinical Genetics Branch Division of Cancer Epidemiology and Genetics National Cancer Institute, National Institutes of Health 9609 Medical Center Drive Rockville Maryland 20850.
authors.forename: Blanche P
authors.initials: BP
authors.lastname: Alter
authors.affiliation: Clinical Genetics Branch Division of Cancer Epidemiology and Genetics National Cancer Institute, National Institutes of Health 9609 Medical Center Drive Rockville Maryland 20850.
authors.forename: Sharon A
authors.initials: SA
authors.lastname: Savage
keywords: Bone marrow failure; diagnosis; dyskeratosis congenita; qPCR; telomere