Volume 8, Number 5—May 2002
Sentinel Surveillance: A Reliable Way To Track Antibiotic Resistance in Communities?
|Area||Actual %PNSP (target range)||No. of isolates needed to estimate %PNSPa||% of sentinel groups of 5 laboratories with > no. of required isolates|
a No. of isolates, n, required to estimate the area’s actual %PNSP (P) within 5 percentage points (d=0.05) with 95% confidence (Z=1.96) is: n= (Z2 P(1-P))/d2, where d is the range of accepted variation around the actual %PNSP, and Z is the Z-score range within which values must fall. Because the total no. of isolates per area, N, was small, we corrected this estimate for finite population size: n=n/[1+(n-1)/N]. There is no power associated with this estimate (14).
%PNSP, percent of penicillin-nonsusceptible pneumocooccal isolates.