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posted by on Monday December 12 2016, @07:44AM   Printer-friendly
from the reporting-slipped-our-minds dept.

Science magazine reports:

A far higher number of babies in Colombia have developed microcephaly related to Zika virus infections than previously reported. [...] It now appears that incomplete reporting may explain some of the disparity.

[...] the CDC and Colombia's ministry of health and national institute of health, offers "preliminary information" about 476 cases of microcephaly identified over the last 11 months. In contrast, the latest World Health Organization (WHO) "situation report", with data current to 7 December, said that Colombia had only reported 60 cases

[...] Zika is probably not to blame for all of the 476 cases. The paper reports that 306 of the affected babies were tested for Zika virus infection with the ultrasensitive polymerase chain reaction that detects viral RNA or immune markers. Just under half, 147, had evidence of Zika virus infection.

Full paper: https://www.cdc.gov/mmwr/volumes/65/wr/mm6549e1.htm

WHO report (pdf) http://apps.who.int/iris/bitstream/10665/251905/1/zikasitrep8Dec2016-eng.pdf?ua=1


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  • (Score: 0) by Anonymous Coward on Monday December 12 2016, @03:53PM

    by Anonymous Coward on Monday December 12 2016, @03:53PM (#440402)

    This disease where if head circumference were normally distributed, would by diagnosed in 2.5% of the population by definition... and if head circumference is not normally distributed, would have a nonsensical definition:

    Microcephaly is defined as an occipito-frontal head circumference (OFC) 2 or more standard deviations below the mean for age and sex

    https://www.ncbi.nlm.nih.gov/pubmed/2211965 [nih.gov]

    Also, remember that microcephaly does not mean micrencephaly (which is what we actually care about):

    Microcephaly (small head) is clinically important only if there is concomitant micrencephaly (small brain). Extensive studies on patients in mental institutions have shown that there is close correlation among microcephaly, micrencephaly, and mental retardation when the head is more than three standard deviations below the norm. If the small head is less than two standard deviations below the norm, no strong correlation exists with eigher small brain or mental retardation.

    http://www.ncbi.nlm.nih.gov/pubmed/5678001 [nih.gov]

  • (Score: 0) by Anonymous Coward on Monday December 12 2016, @04:03PM

    by Anonymous Coward on Monday December 12 2016, @04:03PM (#440409)

    Also, the antibody tests for zika are not specific at all:
    https://soylentnews.org/comments.pl?sid=14263&cid=367512#commentwrap [soylentnews.org]

    Another thing, the science editorial contains "fake news" about this important aspect, even going so far as to stress the "ultrasensitive" nature of PCR. It says

    "The paper reports that 306 of the affected babies were tested for Zika virus infection with the ultrasensitive polymerase chain reaction that detects viral RNA or immune markers."

    This is wrong, from the report:

    "Specimens are tested for Zika virus RNA by real-time reverse transcription–polymerase chain reaction (rRT-PCR), for serologic evidence of infection by Zika immunoglobulin M (IgM) antibody capture enzyme-linked immunosorbent assay (MAC-ELISA), or for Zika viral antigens by immunohistochemistry
    [...]
    147 (48%) had laboratory evidence of Zika virus infection by RT-PCR or immunohistochemistry"

    https://www.cdc.gov/mmwr/volumes/65/wr/mm6549e1.htm [cdc.gov]

    So only some unspecified percentage were tested with PCR.

  • (Score: 2, Interesting) by shrewdsheep on Monday December 12 2016, @08:56PM

    by shrewdsheep (5215) on Monday December 12 2016, @08:56PM (#440548)

    Actually, it is quite common to define a disease based on quantiles. While indeed the two standard deviations are 2.5% for the normal definition, the definition could have just been the lower 2.5% quantile. The second question would be whether this disease definition is relevant clinically in terms of sensitivity and specificity https://en.wikipedia.org/wiki/Sensitivity_and_specificity [wikipedia.org]. For microcephaly the lower 2.5% group is indeed enriched with children who do have problems (syndromes, infections, placenta problems etc.), however, your correct in pointing out that of course Zika is just one possible cause.

    • (Score: 0) by Anonymous Coward on Monday December 12 2016, @09:39PM

      by Anonymous Coward on Monday December 12 2016, @09:39PM (#440563)

      it is quite common to define a disease based on quantiles.

      And those diseases have nonsensical definitions as well. This has nothing to do with sensitivity and specificity. We are not talking about a test for a disease, we are talking about the definition...

      Also, my point wasn't other causes of microcephaly, it is that both the presence of a disease state and presence of a virus are highly uncertain here. We are getting into psychology-level territory with the threats to internal validity.

      • (Score: 2, Interesting) by shrewdsheep on Tuesday December 13 2016, @04:00PM

        by shrewdsheep (5215) on Tuesday December 13 2016, @04:00PM (#440825)

        Maybe I made myself not clear enough. In the end *all* diagnoses can be viewed as being based on quantiles (e.g. a tumor is diagnosed if tissue growth is in the top quantiles). The level of indirection goes further: a diagnosis can be viewed as a test as to whether more tests should be performed. For *all* diagnoses getting the diagnosis does not mean you have to do anything about it. The diagnosis merely enriches the group with the diagnosis for certain problems. Step by step it is decided whether to investigate further and for this specificity/sensitivity (for giving us information on the next step) are important. At some point you stop when you feel certain enough.

        • (Score: 0) by Anonymous Coward on Tuesday December 13 2016, @04:09PM

          by Anonymous Coward on Tuesday December 13 2016, @04:09PM (#440829)

          In your universe it is impossible to ever reduce the rate at which a disease is diagnosed, the goal posts will just constantly move so that 2.5% (or whatever) people always must have the disease. Sounds like a great scam!