Table 3.

Screening methods employed to measure trinucleotide repeat length. Relative advantages and disadvantages of methods used to measure repeat length and instability.

	Southern blot	STR analysis	SP-PCR	TP-PCR	No-Amp
PCR dependent		✓	✓	✓
High total DNA input requirement	✓				✓
Repeat size estimate	✓	✓	✓	✓
Labour intensive	✓		✓
Detection of >130 repeats	✓		✓	✓*	✓
Sequence level resolution					✓
Detection of biallelic expansions	✓	✓**	✓	✓*	✓
Detection of allele level instability			✓		✓

STR, Short tandem repeat; SP-PCR, Small pool-polymerase chain reaction; TP-PCR, Triplet repeat primed-polymerase chain reaction; *, Only allows presence or absence detection at >130 repeats; **, Only if both alleles are <130 repeat.