FISH vs. CGH: Key Differences, Accuracy, and When to Use Each Genetic Test
FISH (Fluorescence In Situ Hybridization) pinpoints specific DNA regions with glowing probes; CGH (Comparative Genomic Hybridization) scans the entire genome for gains and losses in one pass.
People mix them up because both light up chromosomes on a slide, yet FISH tells you “yes or no” for a known mutation, while CGH quietly counts extra or missing pieces across every gene, like watching a single star versus scanning the night sky.
Key Differences
FISH needs prior suspicion and a labeled probe for each target; CGH compares patient and reference DNA without knowing what to look for, detecting microdeletions and duplications genome-wide in a single hybridization.
Which One Should You Choose?
Order FISH when you already suspect a specific microdeletion like DiGeorge or HER2 amplification; pick CGH for unexplained developmental delay, autism, or miscarriage where the culprit could hide anywhere on any chromosome.
Can one test replace the other?
No. FISH confirms known variants fast; CGH discovers new ones but misses balanced rearrangements.
How long for results?
FISH: 24–48 hours. CGH: 7–14 days.