Tracking type specific prevalence of human papillomavirus in cervical pre-cancer: a novel sampling strategy.
BACKGROUND
Surveillance designed to detect changes in the type-specific distribution of HPV in cervical intraepithelial neoplasia grade 3 (CIN-3) is necessary to evaluate the effectiveness of the Australian vaccination programme on cancer causing HPV types. This paper develops a protocol that eliminates the need to calculate required sample size; sample size is difficult to calculate in advance because HPV's true type-specific prevalence is imperfectly known.


METHODS
A truncated sequential sampling plan that collects a variable sample size was designed to detect changes in the type-specific distribution of HPV in CIN-3. Computer simulation to evaluate the accuracy of the plan at classifying the prevalence of an HPV type as low (< 5%), moderate (5-15%), or high (> 15%) and the average sample size collected was conducted and used to assess its appropriateness as a surveillance tool.


RESULTS
The plan classified the proportion of CIN-3 lesions positive for an HPV type very accurately, with >90% of simulations correctly classifying a simulated data-set with known prevalence. Misclassifying an HPV type of high prevalence as being of low prevalence, arguably the most serious kind of potential error, occurred < 0.05 times per 100 simulations. A much lower sample size (21-22 versus 40-48) was required to classify samples of high rather than low or moderate prevalence.


CONCLUSIONS
Truncated sequential sampling enables the proportion of CIN-3 due to an HPV type to be accurately classified using small sample sizes. Truncated sequential sampling should be used for type-specific HPV surveillance in the vaccination era.
The Kirby Institute, The University of New South Wales, Sydney, Australia. ewaters@kirby.unsw.edu.au
Edward K
EK
Waters
John
J
Kaldor
Andrew J
AJ
Hamilton
Anthony Ma
AM
Smith
David J
DJ
Philp
Basil
B
Donovan
David G
DG
Regan
D001315:Australia; D015982:Bias; D003198:Computer Simulation; D003627:Data Interpretation, Statistical; D005260:Female; D006801:Humans; D030361:Papillomavirus Infections / Q000145:classification / Q000453:epidemiology* / Q000821:virology; D053918:Papillomavirus Vaccines / Q000008:administration & dosage; D011159:Population Surveillance / Q000379:methods*; D011230:Precancerous Conditions / Q000473:pathology / Q000821:virology; D015995:Prevalence; D015203:Reproducibility of Results; D018401:Sample Size; D020711:Threshold Limit Values; D002578:Uterine Cervical Dysplasia / Q000145:classification / Q000453:epidemiology*
D053918:Papillomavirus Vaccines