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I am having difficulties understanding the following table from the study Incidence and clearance of genital human papillomavirus infection in men (HIM): a cohort study.

I think I might be reading the below table completely wrong, but am I right with the following - let's take the row for HPV type 51 for example:

  1. 72 men tested positive at the first test of the study for HPV type 51? (prevalence)
  2. 108 other men (not including the 72 men who tested positive at the start of the study) tested positive for HPV type 51 at some point in time during the 4 years of the study. (incident infections)
  3. Those in sum 180 HPV type 51 positive men tested in sum 91 more times positive for HPV type 51 (new infections)
  4. Of those 180 HPV type 51 positive men 62 infections were cleared. (Cleared infections)

If not, could anybody explain how to make sense of this table?

Full Table Link below https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3231998/table/T2/?report=objectonly

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It says in the methods (under statistical analysis):

For estimates of any or type-specific HPV incidence, only participants who were free of any or a specific HPV type, respectively, at enrolment were included. Since multiple infections are possible within an individual, multiple positive tests were judged as a separate event.

So:

  1. Yes - 72 people out of the study population had an infection for that subtype.
  2. No - the 72 are included in the 108 as multiple (i.e. repeat) infections are counted as individual events, so all of the 72 had the infection, some >1 time.
  3. As above - repeat infections.
  4. Yes, as above - infection, cleared, re-infection. Sometimes more than one infection for 1 individual in the study period.
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  • Thank you, I still don't quite get what the difference between "Incident Infections" and "New Infections" is though.
    – ytg7
    Jan 17, 2022 at 8:55
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    Incidence is number infected from study population (though usually expressed as per 100,000 or similar) New infections is the number of observed infections, assuming clearance between tests. I personally think this is a poor measure, you shouldn't do both really, especially when we know these are often persistent infections, so the "new infections" is a bit of a made-up statistic as they don't know about the status between tests, even from patient observational data.
    – bob1
    Jan 17, 2022 at 19:20
  • Ok I think I get it, just one last thing to clarify: so if a person tests postive for a specific type on the first test, comes back 6 month later for follow up test and tests positive for the same type again, comes back 6 month later for follow up and again tests positive for the same type that would be +1 to incident infections and +3 to new infections. Or would that be only +2 to new infections, because the first test at enrollment of the study doesn't count as new infection?
    – ytg7
    Jan 18, 2022 at 8:48
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    @ytg7 good question - I don't know the answer to that. I suspect the latter scenario of the first test not counting as a new infection.
    – bob1
    Jan 18, 2022 at 20:21

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