Methods of determining the length of a multinucleotide repeat region in a target nucleic acid are provided herein which include labeling amplified target nucleic acids with a target detection label independent of the number of multinucleotide repeats and a repeat-detection label proportional to the number of multinucleotide repeats, wherein the two types of labels are each independently incorporated in the amplified target nucleic acids during the amplifying or after the amplifying; binding the amplified target nucleic acids to a capture probe specific for the amplified target nucleic acids; detecting the target detection label associated with the capture probe to produce a first signal; detecting the repeat-detection label associated with the capture probe to produce a second signal; and determining a ratio of the first signal and the second signal, wherein the ratio is indicative of the length of the multinucleotide repeat region in the target nucleic acid.