Calculation of the number of HIV positives in the window period.

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Dear Friends,

Please help me in calculation of the number of HIV positives in the window

period. Let us assume that: Population of the target group = p

Sero-prevalence in the target group = s

Estimated number of HIV infections in the target group = sxp/100

= sp/100

No. of people in the window period = w

Depending on the sero prevalence the number of people in the window period

(w) would differ. It would be negligible where the sero-prevalence is very

low say below 0.5 percent. But in target groups where the sero-prevalence is

very high 10 % and above the number of people in the window period will not

be negligible.

I would like to:

1) Get feedback whether the above assumptions are so far correct and

applicable to ultimately calculate the number of infections from

blood donors in the window period?

2) Know if there is some literature available to calculate the number of

people in the window period, once we know the values for p, and s. If not

has anyone a clue as to how to do it.

3) Are more variables required to calculate w?

Looking forward to your clarifications and feedback. Thanking you,

With warm regards,

Yours sincerely,

Dr. E. Mohamed Rafique

General Hospital, Tata Tea Ltd.,

Munnar - 685 612. Idukki District, Kerala, INDIA.

Tel: +91 486-531306 (Office) and +91 486-531457 (Residence)

Fax: +91 486-530333 and +91 486-530152

E-mail: emrafi@... and ish@...

URL: http://www.ishima.info

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