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NanoLogix Inc. Message Board

  • omarhatesyoutube omarhatesyoutube Feb 26, 2013 4:33 AM Flag

    Test results, what the numbers mean, explained

    I might as well be the one to start the DD for the pumpers.

    Regarding the test results.

    Reported 97.1% sensitivity, this means that the test correctly identified 97.1% of all patients that had GBS. Meaning 2.9% of patients that did have GBS were not detected by the device.

    The test also had a specificity of 88.4%. meaning the test incorrectly gave a positive reading for 11.6% of patients tested.

    Here are my concerns. 11.6% false positives, is a pretty big deal when the general population you are dealing with only has GBS on average of ~15% of the time. This means that of all the patients this test flags for GBS.

    About 1/3 will in fact not have GBS.

    Let's make this simpler. And say we test 1000 patients in the hospital with the quick test for GBS.

    Let's assume that 150 have GBS.

    Here are the results form using nanologix product.

    145 of the 150 patients who had GBS were identified, 5 were missed.

    However.. 102 patients who DID NOT ahve GBS were also identified as having GBS, incorrectly.

    752 patients who did not have GBS were reported by the test to not have GBS (5 of those did have it)

    Inter-observer reliability is rather insignificant suggesting very small user error, maybe a few patients out of that result would differ between two separate technicians. This also means most likely any errors were technology based and not methodology based or user based, unless those conducting the test did the entire thing wrong form the start. And yes I checked the sensitivity and specificity rates for the control.. and it is 100% or 99.8%+ So there really is little room to blame the control testing.

    Now regarding FDA approval (honestly I do not even know if this needs fda approval I guess that is your ball park) I read several reports of different type of testing tools that got and were denied FDA approval. 96-100 is the range the approvals typically fell in. However 99.8%+ is preferred and the FDA even rejected many tests with 99% sensitivity. However the real problem I fear here is the specificity with being almost half patients tested are incorrectly identified vs correctly identified. The FDA would not approve this in my opinion, as I can not find any other approvals during my cursory search that had anywhere near that level of error.

    Sorry if taht is not what you want to hear.

    Is there some better hope for nanologix newer tests. I hope so, because imo.. this does not look good. Or maybe they can refine the methodology. Or perhaps there is a situation where they do not care about false positive tests. Such as using some other advanced fast test first. Then using nano's product to get a quicker culture? Although to be honest 97.1% is really at the low end of sensitivity that could get FDA approvals. And FDA approval is no cake walk.

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    • It's funny when someone who clearly knows very little about science, as evidenced by all your posts today, starts a whole topic related to it, in my opinion. Thanks for the comedy, needed that. Some of us actually work in this field and find posts like this hilarious.

      • 1 Reply to the_rail_splitter
      • Cool story bro. imo you and parents and the like are full of ****

        It is clear no productive discussion will be accomplished here. I'll just leave then, i don't need nor want an army of people following me around to other boards and down votinga ll my postings out of spite. Talk about childish.

        I only hope you come to your sense before you loose everything. I won;t be back, have fun with your games and good luck

    • "The test also had a specificity of 88.4%. meaning the test incorrectly gave a positive reading for 11.6% of patients tested."

      No, doesn't it mean that 11.6% of the positives flagged were false positives, not that it flagged 11.6% of ALL cases as positive?

      "This means that of all the patients this test flags for GBS. . . . About 1/3 will in fact not have GBS."

      Aren't you double-counting, or multiplying the specificity error rate by the % of population who have GBS? Shouldn't your statement be amended to say, "This means that of all the patients this test flags for GBS. . . . About 11.6% will in fact not have GBS." If I am not following correctly, my apologies.

    • And I'll start for the bashers
      From the publication from march 2012
      We have found that by adding bacitracin to each washing step, one
      may greatly reduce interference with Enterococcus. While this allowed
      for the increased specificity found when samples were retested, it
      should be noted that there were still 7 samples that were positive by
      the rapid test but negative by traditional culture. While it is possible
      that these samples may have additional contaminants causing the
      results to be persistently falsely positive, it may be possible that a GBS
      non–beta-hemolytic variant would be missed by traditional culture
      but detected by the antibody-based rapid test. Indeed, one of these
      samples was confirmed to contain GBS by PCR.

      Andre

    • What is the danger of getting a false GBS positive? The patient gets an unnecessary course of antibiotics. Guess what? That's just what's happening now, antibiotics being given as a precaution because the docs can''t be sure if the patient has GBS. So, even if you're right, this technology substantially curtails that problem but does not eliminate it completely. I would call that substantial progress.

    • There are many testing procedures currently in use that are much less conclusive. You did a good job of crunching the numbers but I think you lack any industry specific knowledge.

 
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