Tables for the cytogenetic study of fragile X chromosomes for diagnostic purposes.

The frequency of expression of the fragile X chromosome varies from patient to patient. Many cases have been reported showing frequencies of less than 2%. With such low frequencies, the risk of erroneous diagnosis is great unless the appropriate number of cells is studied. We present here Tables based on the binomial distribution relating the frequency of expression of the fragile X in a patient with the sample size required to obtain a probability P of correct diagnosis according to different criteria.