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Thread: Different Match Results on Different Platforms

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    Different Match Results on Different Platforms

    I came across the fact that the very same matches get very different shared lengths of DNA depending on the platform I look at. Recently I also read that AncestryDNA might use more filters to provide the user with valid matches and therefore produces lower results in cM and segments sometimes. Can anyone confirm this and provide more detailed information about the reasons and methods behind these differences? How much can be attributed to the chip, the general algorithm, specific filters or simple errors? Because in some cases the difference is quite big, like three times the shared DNA, which is something.

    Another related question is, whether transferred DNA, like from 23andme chip V3 to FTDNA, can reduce the shared DNA in comparison to a test done on the platform itself? Has anyone experiences with first a transfer and then a later sample from the platform itself?

    Probably someone knows the answers, because a quick Google search returned not enough.

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    Different rules for the minimum segment length mostly I'm guessing. There's one match on 23andMe I share only 32cM/4 segments, on AncestryDNA he's 40cM/5 segments and on FTDNA he's 200cM/40 segments. I generally share more with my matches on AncestryDNA than 23andMe, but they are still close, and way more with some of my matches on FTDNA than any other site.

    I'm not sure how up to date the information is on this site, but it would probably lead to better insight: https://isogg.org/wiki/Autosomal_DNA_match_thresholds
    Code:
    23abc_AncestryDNA_scaled,0.110408,0.151314,-0.0290383,-0.0507112,0.0018465,-0.0156179,-0.00305514,-0.00138456,-0.00899905,0.00911181,0.00243583,-0.00149867,-0.00431116,0.00344057,-0.00773606,0.00106072,0.00195576,0.00152026,0.00251396,-0.00550264,-0.00786113,-0.00197844,0.0025882,0.00168699,0.000957998

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     Riverman (10-26-2020)

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    Quote Originally Posted by 23abc View Post
    Different rules for the minimum segment length mostly I'm guessing. There's one match on 23andMe I share only 32cM/4 segments, on AncestryDNA he's 40cM/5 segments and on FTDNA he's 200cM/40 segments.
    I have cases with the same numbers of segments, but they have much more cM on 23andme (2-3 times) than on Ancestry, FTDNA or MyHeritage and vice versa. So apparently there is no rule as to where our matches score more, if I compare with your case. What else could be the reason?

    Also, is the higher number of shared DNA always the more likely, more reliable result?
    Last edited by Riverman; 10-26-2020 at 10:52 AM.

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    Quote Originally Posted by Riverman View Post
    I have cases with the same numbers of segments, but they have much more cM on 23andme (2-3 times) than on Ancestry, FTDNA or MyHeritage and vice versa. So apparently there is no rule as to where our matches score more, if I compare with your case. What else could be the reason?

    Also, is the higher number of shared DNA always the more likely, more reliable result?
    Better than that, the most reliable thing is having more than 10 cM in the bigger segment.

    I have noticed also my matches in 23andMe the minimum shared segment have more or less 10 cM, in My Heritage I have matches with 6 cM, these are less reliable and have more posibilites that they are falses.
    23andMe: 99.4% Spanish & Portuguese, 0.3% Ashkenazi Jewish, 0.3% Trace Ancestry (0.3% Nigerian)

    My Heritage: 91.5% Iberian, 3.6% Ashkenazi Jewish, 2.7% Middle East, 2.2% Irish, Sccotish and Welsh

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     Riverman (10-26-2020)

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    Quote Originally Posted by rober_tce View Post
    Better than that, the most reliable thing is having more than 10 cM in the bigger segment.

    I have noticed also my matches in 23andMe the minimum shared segment have more or less 10 cM, in My Heritage I have matches with 6 cM, these are less reliable and have more posibilites that they are falses.
    That's true, but for some of these matches, even the biggest shared segment varies in size. So there is something about the recognition and assignment which is different or can go wrong.

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     rober_tce (10-26-2020)

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