Correlation between an early 6 and early 7 oncogenes detection method and conventional cytology for cervical cancer screening at Kenyatta National Hospital, Kenya
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The oncogenic potential of human papilloma virus (HPV) early genes E6 and E7 is of interest in HPV testing for cervical carcinoma. The current study included women less than 40 years attending the Kenyatta National Hospital family planning clinic, with an objective of comparing the performance of cytological tests done in Kenya with the Pretect SEE assay developed by Norchip AS (Norway). Two hundred and four (204) samples were obtained in which the HPV E6 and E7 HPV mRNA was evaluated using the Pretect SEE assay for detection of high risk HPV types 16, 18 and 45. The HPV 35 and 52 may not be involved as the cause of invasive cervical cancer in Kenya. The real-time nucleic acid sequence-based on amplification was also included. The Pap test and cytological analysis were done locally at the Kenyatta National Hospital and the results were recorded and compared to the Pretect SEE results. Three (3) out of two hundred and four (203) women were positive with Pretect SEE (samples that expressed E6 and E7 HPV oncogenes), whereas only one sample(1) out of two hundred and three 203 samples was positive with Pap test. One sample (1) was rejected due to lack of cells. The overall diagnostic prevalence of HPV was 1.47% (3/203) after testing with pretect SEE and 0.5% (11203) after testing the pap smears. The Pretect SEE showed a specificity of 100% and a sensitivity of 100% using Pap smear as Gold standard. The PreTect SEE showed a positive predictive value (PPV) of 33 % and a 99% negative predictive value using Pap smear as the gold standard. The Pap smear showed a specificity of 100% and a sensitivity of 33% when using PreTect SEE as the gold standard. If all the PreTect SEE contains CIN2+ cases, the sensitivity, specificity, PPV and NPV would be 100%. In conclusion, the Pretect SEE™ assay was found to be more sensitive than the Pap smear. Therefore the use of PreTect SEE as a primary screening method with a high coverage rate may reduce the incidence of cervical pre-cancer to a minimum in Kenya. Using a very sensitive and specific method in a very representative female population in Kenya has strongly indicated that the prevalence of cervical cancer in Kenya may be lower due to false positive and lack of differentiation between transient and transforming infections. The estimated number of annual cervical cancer cases may be around 1000 and not 4800 as indicated by the IeO HPV Information (2012). The estimated prevalence of HPV 16 and/or HPV 18 DNA (2012) reported by ICO HPV Information Centre among cytological women in Kenya, may be less than 2,5%and not 9.1%. Around 40% of the HPV 16 and 18 HPV DNA in cytological normal cases may not express E6 and E7 mRNA. This also show that the prevalence of HIV in the whole Kenya population may not be 6.2% but rather less than 2%. The study showed that it is important to perform national screening in more than 3.2% of typical national population's in Africa.