About the letter “Comments on the article, “Software for Y-Haplogroup Predictions, a Word of Caution”

Abstract

Dear Sirs: The letter by Dr. Athey entitled “Comments on the article, “Software for Y-Haplogroup Predictions, a Word of Caution” discusses a paper of our authoring in the present Journal [1]. Though at first glance his opinion may seem reasonable, a careful analysis reveals a series of mistakes committed by Dr. Athey. In the mentioned letter, one of the main concerns of Dr. Athey is the amount of short tandem repeats (STRs) that were analyzed. He comments that seven markers should be avoided, explaining that an increase of that amount augments the probability of assignment, stating that “With the addition of a sufficient number of markers, the prediction probability for the correct haplogroup can be ‘driven’ past 99% in nearly all cases, and this almost always occurs by the point where 20 markers have been used.” Nonetheless, he does not make reference to any sort of validation study, so said 99% must only refer to the probability of assignment his own software provides. What is more, Dr. Athey seems oblivious that our paper examined this software’s predictive values in different cutoff points, up to 95% of probability of assignment, still obtaining inadequate predictive values on said cutoff point. Twelve of our haplotypes proposed from 100% to 99.6% probability of assignment to the R1b haplogroup in the Haplogroup Predictor, while none of those samples belong to the said haplogroup. In the R haplogroup, one haplotype gives 99.8% probability to an erred haplogroup (E1b1b), while 14 give from 100% to 99.4%, assigning these samples to the R1b haplogroup, and were considered as correct predictions. Note that in these cases, the predicted haplogroup follows the nomenclature of the software, and the probability was not pooled by major branches. If the seven markers of the minimal haplotype were not a proper set, Dr. Athey’s software should not provide such high probabilities of assignment in these cases, since it misleads the user. Unfortunately, Dr. Athey’s mention that seven Y-STRs are too few occurs only in his letter; neither of the two papers of his authoring [2, 3] available at the Haplogroup Predictor’s website (http:// www.hprg.com/hapest5/) nor the software instructions (http://www.hprg.com/hapest5/page4.html) explain that the user should employ more than seven markers. Otherwise, we would not have attempted to use it. Moreover, a simple glance at recent literature where the Haplogroup Predictor was employed clearly shows that researchers do not use such high amounts of Y-STRs when they rely on the Haplogroup Predictor; for instance, Salas et al. [4] used the seven Y-STRs we did, plus DYS 385 and Petrejcikova et al. [5] only 12 Y-STRs. His statement “...indeed, the seven-marker dataset apparently resulted from a study carried out over five M. Muzzio :V. Ramallo : J. M. B. Motti :M. R. Santos : J. S. Lopez Camelo :G. Bailliet Laboratorio de Genetica Molecular Poblacional, Instituto Multidisciplinario de Biologia Celular (IMBICE), CICPBA, CCT, La Plata–CONICET, La Plata, Argentina