Test Details: FISH is a more sensitive method for detecting CML than the standard cytogenetic tests that identify the Ph chromosome. Isochromosome 17q [i(17q)] with its two identical long arms is formed by duplication of the q arm and loss of the short p arm. Iso 17q is detected either as a single abnormality or as a part of a complex karyotype, which additionally influences its prognostic significance and makes the results of research unclear.