A comparative analysis of conventional Pap smear cytology, liquid based cytology and colposcopy clinical impression with colposcopy biopsy histology as gold standard in women undergoing colposcopy in Kenyatta National Hospital
Keywords:Cervical, Cancer, Screening, Pap smear, Liquid-based cytology, Colposcopy biopsy histology, Sensitivity, Specificity, Predictive value
Background: Cervical cancer is one of the most common female malignancies worldwide. Since the introduction of conventional Papanicolaou smear mortality from cervical cancer has reduced considerably. Despite its success, it has sensitivity of only 51% and false negative rate of 5-10%. Approved liquid based cytology (LBC) products by FDA claim a 65-percent increased detection rate of high grade squamous intraepithelial lesions (HGSIL) compared with conventional smears, as well as decreased unsatisfactory sample rates. Evidence shows that liquid based preparation is more sensitive and accurate for the detection of both squamous and glandular lesions of the cervix. Studies of the accuracy of liquid based preparations reports sensitivity of 61-66% and specificity of 82-91%. Objective of current study is to compare the performance of conventional Pap smear cytology, liquid based cytology and colposcopy clinical impression with colposcopic biopsy as the gold standard among women eligible for colposcopy in Kenyatta National Hospital, Kenya.
Methods: This was a hospital-based comparative cross-sectional study. Convenient sampling over a period of 4 months was used to recruit clients referred to colposcopy clinic with abnormal Pap smear results.
Results: A total of 73 patients referred with abnormal pap smears were recruited into the study. The mean age of the patients was 38 yrs (SD ±10). About 45% of the patients interviewed did not have knowledge of Pap smear testing. Both the results of referral Pap smear and repeat Pap smear were predominantly low grade squamous intraepithelial lesions (LGSIL) or HGSIL. With biopsy results being the gold standard, Liquid based cytology had a higher specificity of 75% when compared with conventional pap smears’ 11%.
Conclusions: Even though colposcopy clinical impression has the highest agreement with colposcopy biopsy it’s a diagnostic and not a screening test, hence Liquid based cytology showed better performance as a screening test compared to conventional Pap smear. In general, there was good agreement for cytological results of repeat CPAP and LBC. We therefore recommend that for patients referred with abnormal pap smears requiring a repeat pap smear, liquid based cytology is used due to its higher specificity compared to conventional Pap smear.
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