Interlaboratory comparison of autoradiographic DNA profiling measurements. 3. Repeatability and reproducibility of restriction fragment length polymorphism band sizing, particularly bands of molecular size > 10K base pairs.

The observed interlaboratory standard deviation (SD) associated with the restriction fragment length polymorphism (RFLP) measurement of DNA fragment size is a predictable function of the observed mean band size (MBS). For DNA fragments of size 1,000 base pairs (bp) to the largest resolved component of commonly used "sizing ladder" calibration materials (about 20,000 bp), the variation in the sizing data from the Technical Working Group on DNA Analysis Methods (TWGDAM)-sponsored "Large Fragment Study" is well-described by SD = 7.5 (1 + MBS/19 500)7.1. This sizing variability arises from a 0.1-0.4% SD in the relative positions of sample and calibration bands among electrophoretic gels. Statistically significant sizing differences do exist for bands above 10,000 bp among laboratories that use different calibration materials. The Large Fragment Study was efficiently accomplished through the use of a designed set of DNA samples, requiring but one gel in each of 20 participating laboratories.