|Year : 2018 | Volume
| Issue : 1 | Page : 80-83
Comparison of conventional Pap smear and liquid-based cytology: A study of cervical cancer screening at a tertiary care center in Bihar
Sangeeta Pankaj1, Syed Nazneen1, Simi Kumari1, Anjili Kumari1, Anita Kumari1, Jaya Kumari1, Vijayanand Choudhary2, Shishir Kumar3
1 Department of Gynecological Oncology, IGIMS, Patna, Bihar, India
2 Department of Pathology, IGIMS, Patna, Bihar, India
3 Department of Biostatistics RCC, IGIMS, Patna, Bihar, India
|Date of Web Publication||23-Aug-2018|
Dr. Sangeeta Pankaj
Department of Gynecological Oncology, IGIMS, Patna, Bihar
Source of Support: None, Conflict of Interest: None
Background: Cervical cancer is the fourth leading cause of cancer in women in the world and it is the second most common cancer in women 15–44 years of age. Strict implementation of screening programs has led to a large decrease in cervical cancer incidence and mortality in the developed countries. In contrast, cervical cancer remains largely uncontrolled in high-risk developing countries because of ineffective or no screening programs. Conventional Pap smear method has been the mainstay of most of the screening programs for many decades. However, this technique is not without limitations, and the sensitivity and specificity of cervical cytology are relatively low. To overcome the limitations of conventional Pap smear (CPS), liquid-based cytology (LBC) was introduced in 1990s as a better tool for processing cervical samples. Objectives: This study was undertaken to compare CPS with liquid-based methods, to assess the effectiveness and feasibility of LBC over CPS in our setting, and also to evaluate the prevalence of human papillomavirus (HPV) in our population. Materials and Methods: This study was conducted in Gynecological Oncology Unit of Regional Cancer Center at Indira Gandhi Institute of Medical Sciences, Patna, Bihar. About 310 women were enrolled in this study and the sample was taken for both conventional cytology and LBC. The smears were studied in detail and were interpreted as per the Bethesda system of reporting Pap smears. The results were compared and analyzed statistically. Results: Unsatisfactory smears were more commonly reported by conventional method (7.1%) than with liquid-based method (1.61%), and this difference is statistically significant. There was no difference in the detection of epithelial cell abnormalities using both the methods. HPV DNA for high-risk oncogenic strains (16 and 18) was detected in 6.45% of women in this study. Conclusion: LBC has been found to be more superior to conventional smears only with respect to lesser number of unsatisfactory smears, but considering the economic implications of LBC, conventional Pap is more feasible in our setting.
Keywords: Cervical cancer screening, conventional Pap smear, human papillomavirus, liquid-based cytology
|How to cite this article:|
Pankaj S, Nazneen S, Kumari S, Kumari A, Kumari A, Kumari J, Choudhary V, Kumar S. Comparison of conventional Pap smear and liquid-based cytology: A study of cervical cancer screening at a tertiary care center in Bihar. Indian J Cancer 2018;55:80-3
|How to cite this URL:|
Pankaj S, Nazneen S, Kumari S, Kumari A, Kumari A, Kumari J, Choudhary V, Kumar S. Comparison of conventional Pap smear and liquid-based cytology: A study of cervical cancer screening at a tertiary care center in Bihar. Indian J Cancer [serial online] 2018 [cited 2019 May 25];55:80-3. Available from: http://www.indianjcancer.com/text.asp?2018/55/1/80/239588
| » Introduction|| |
Across the globe, there are 2784 million women aged 15 years and older who are at risk of developing cervical cancer, and about 527,624 new cervical cancer cases are diagnosed annually. Cervical cancer ranks as the fourth leading cause of cancer in women worldwide, and it is the second most common cancer in women between 15 and 44 years of age., Almost 70% of the global burden of cervical cancer falls in areas with lower levels of development, and more than one-fifth of all new cases are diagnosed in India. For women in India, cervical cancer is the second most common cancer. Cervical cancer is also the second most common cause of cancer deaths when both genders are combined.
“Cervical cancer can have devastating effects with a very high human, social, and economic cost, affecting women in their prime. But this disease should not be a death sentence, even in poor countries,” explains Dr. Rengaswamy Sankaranarayanan, a lead investigator for an IARC research project with a focus on cervical cancer screening in rural India. “Low-tech and inexpensive screening tools exist and could significantly reduce the burden of cervical cancer deaths right now in less developed countries.”
Sexually transmitted human papillomavirus (HPV) infection is the most important risk factor for cervical intraepithelial neoplasia (CIN) and invasive cervical cancer. Worldwide, the prevalence (%) of HPV 16 and/or HPV 18 among women with normal cytology is 4.1%. HPV serotypes 16 and 18 account for nearly 76.7% of cervical cancer in India. Globally, high-risk types HPV 16 and 18 contribute to more than 70% of all cervical cancer cases.
Frequently performed cytology screening programs have led to a decline in cervical cancer incidence and mortality in developed countries. In contrast, cervical cancer remains largely uncontrolled in high-risk developing countries because of ineffective or no screening program.
Pap smear More Details is the most effective method for the prevention and detection of cervical cancer, but the accuracy of this important screening tool remains controversial. Several recent meta-analyses have reported quite low Pap smear sensitivities – in the range of 50% but as low as 20%.,
To overcome the limitations of conventional Pap smear (CPS), liquid-based cytology (LBC) was introduced in 1990s as a better tool for processing cervical samples. This study compares CPS method and LBC at a tertiary care center in Bihar.
| » Materials and Methods|| |
This study was conducted at Indira Gandhi Institute of Medical Sciences, a tertiary care center in Bihar, over a period of 6 months. A total of 310 consenting patients who fulfilled the inclusion criteria were enrolled in the study. Sexually active women between 20 and 75 years of age were included. Pregnant women, women with active vaginal bleeding, hysterectomized women, and women with frank growth and/or who had never been sexually active or had undergone prior treatment for CIN or cancer cervix were excluded from the study. A detailed proforma including all basic information and details about complaints was filled out for each patient. These women then underwent a gynecological examination. At the beginning of the examination, a cytobrush was introduced into the external cervical os and scraped to collect cells from ectocervix and endocervix. A smear was made on a glass slide for CPS and fixed. The cytobrush was then dropped in a vial containing the preservative fluid for LBC and HPV DNA testing. Conventional cytology and biopsy reporting was done in our hospital, and LBC analysis along with HPV testing was done in a referral laboratory. Cytology was reported using Bethesda system and histology reporting was done using CIN terminology.
| » Results|| |
The most common age group in this study was 31–40 years (39%). About 44% of women were illiterate, and 27% were barely literate. Only 29% women had primary education and above. Many (146; 47.1%) belonged to lower socioeconomic profile. Around 56% of women had three or more children. The most common complaint was excessive vaginal discharge. On speculum examination, the cervix was normal looking in 162 (52.3%) women; in 81 women (26.12%), ectopy was seen; and in the remaining, hypertrophy/polyp/congested cervix were present.
Epithelial cell abnormalities were seen in nine (2.9%) cases using CPS technique and in 12 (3.87%) cases using LBC method, and this difference was not statistically significant.
HPV DNA for high-risk oncogenic types was positive in 20 women (6.45%) in this study. The test was positive in 5.37% of women with normal cytology and in 28.57%–50% of cases with epithelial cell abnormality.
| » Discussion and Conclusion|| |
Pap smear is a very important and useful method for cervical cancer screening. Globally, efforts to prevent the disease include screening women using Pap smears and treating precancerous lesions. Impressive results have been achieved in reducing cervical cancer incidence and mortality in some developed countries by Pap smear screening. Cervical cancer incidence can be reduced by as much as 90% where screening quality and coverage are high. However, in developing countries – where approximately 80% of all new cases occur – many women have never had a Pap smear. Proper implementation of screening programs is essential to reduce the incidence and mortality of cervical cancer in India.
Periodic screening (irrespective of the method used) and follow-up evaluation of women 30 years of age or more are acceptable and cost-effective approaches to prevent cervical cancer. A Pap smear is a cytological test designed to detect abnormal cervical cells. The low sensitivity of a single Pap test makes it necessary to screen women relatively frequently, every 3–5 years.
LBC is the first major change in preparation method for cervical screening samples for more than 50 years. In this method, the cells are washed into a vial of liquid and filtered, and the sample is prepared as a thin layer on a glass slide. These slides are either screened by skilled person or are subjected to automated imaging. This process is being widely used in the United States, European countries, and many other developed nations. Although these approaches appear promising, they are expensive and rely heavily on technology.
LBC is as sensitive as conventional cytology and has other advantages. In the United Kingdom, using implementation of LBC for screening, it has been possible to achieve reduced rates of inadequate samples and increased screening capacity. LBC also provides a platform for HPV testing, automation, and other new technologies. The advantages of decreased screening time by LBC and faster reporting result in lesser anxiety among the women being tested.
In this study, a large proportion belonging to lower socioeconomic strata, and 56% of the women had three or more children – all these factors are documented as risk factors of cervical carcinoma suggesting that our population is at high risk for cervical cancer, and screening needs to be implemented in a proper manner.
Unsatisfactory rate of CPS in our study was 7.1% and it was 1.61% for LBC, and this difference is statistically significant [Table 1]. Similar result is noticed in many previous studies. LBC leads to almost complete elimination of most of the causes for unsatisfactory conventional preparation, with scant cellularity remaining as the main cause for unsatisfactory LBC. In a study by Singh et al., 4.3% smears were reported as unsatisfactory by conventional method and 1.7% smears unsatisfactory by LBC technique.
|Table 1: Comparison of report of cervical cytology by conventional Pap smear and liquid-based method|
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In our study, the rate of detection for epithelial cell abnormalities was similar using both CPS (2.9%) and LBC (3.87%) [Table 2]. Several other studies have documented similar detection rate of epithelial abnormalities by both the methods. In a study by Taylor, performance and accuracy of CPS and LBC were statistically similar. Epithelial abnormalities ranging from atypical squamous cells of undetermined significance (ASCUS) to high-grade squamous intraepithelial lesion (SIL) were seen in 3% and 2% of CPSs and LBCs, respectively. In another study, no statistically significant difference in sensitivity and specificity between the two different methods was reported for detection of CIN2. The randomized trial by Ronco et al. found no significant difference in sensitivity for CIN2 or more with LBC compared with conventional cytology.
|Table 2: Correlation between liquid-based cytology and human papillomavirus DNA reporting|
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In contrast, there are several studies reporting better rate of detection of epithelial cell abnormalities using LBC method. In the cervical cancer screening program of western Sweden, LBC produced a significantly higher yield of histologic high-grade lesions compared with CPSs. Another study reported an increase in the detection of ASCUS by CPS (ASCUS; 3.74% vs. 3.19%) and low-grade SIL (LSIL; 1.67% vs. 1.01%) with a decrease in the ASCUS-to-LSIL ratio from 3.15 for CPS to 2.33 for LBC supporting the use of LBC to enhance the efficiency of cervical cytology screening. A study by Davey showed a significant increase in sensitivity by LBC technique, which detected 1.29 more cases of histological high-grade squamous disease per 1000 women screened than conventional cytology.
HPV DNA test for high-risk oncogenic types was positive in 6.45% of women studied and in 5.37% of women with normal cytology. Globally, the prevalence (%) of HPV 16 and/or HPV 18 among women with normal cytology is 4.1%. Higher percentage of cases (28%–50%) with epithelial cell abnormality was found to be positive for HPV in this study supporting HPV as a causative factor for epithelial abnormality in women. A study in conducted in India concluded that in a low-resource setting, a single round of HPV testing was associated with a significant reduction in the number of deaths from cervical cancer.
LBC can be a better alternative to conventional smear because of lower rate of unsatisfactory smears. Furthermore, residual LBC sample is available to perform HPV DNA testing. LBC with concomitant HPV testing can prove to be more effective in high-resource setting. However, as the detection rate of epithelial abnormalities is similar using both CPS and LBC techniques, CPS is still the best screening method in the Indian scenario with a low-resource setting considering its cost-effectiveness over LBC.
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Conflicts of interest
There are no conflicts of interest.
| » References|| |
Ferlay J, Soerjomataram I, Dikshit R, Eser S, Mathers C, Rebelo M, et al.
Cancer incidence and mortality worldwide: Sources, methods and major patterns in GLOBOCAN 2012. Int J Cancer 2015;136:E359-86.
Bray F, Ren JS, Masuyer E, Ferlay J. Global estimates of cancer prevalence for 27 sites in the adult population in 2008. Int J Cancer 2013;132:1133-45.
Mallath MK, Taylor DG, Badwe RA, Rath GK, Shanta V, Pramesh CS, et al.
The growing burden of cancer in India: Epidemiology and social context. Lancet Oncol 2014;15:e205-12.
PR 223- Latest World Cancer Statistics Global Cancer Burden Rises to 14.1 million New Cases in 2012: Marked Increase in Breast Cancers must be Addressed. IARC; 12 December, 2013.
IARC Working Group on the Evaluation of Carcinogenic Risks to Humans. Human papilloma viruses. IARC Monogr Eval Carcinog Risks Hum 2012;100(Pt B):255-313.
Bruni L, Barrionuevo-Rosas L, Albero G, Serrano B, Mena M, Gómez D, et al
. ICO Information Centre on HPV and Cancer (HPV Information Centre). Human Papillomavirus and Related Diseases in the World. Summary Report; 19 April, 2017.
Cuzick J, Arbyn M, Sankaranarayanan R, Tsu V, Ronco G, Mayrand MH, et al.
Overview of human papillomavirus-based and other novel options for cervical cancer screening in developed and developing countries. Vaccine 2008;26 Suppl 10:K29-41.
Nanda K, McCrory DC, Myers ER, Bastian LA, Hasselblad V, Hickey JD, et al.
Accuracy of the papanicolaou test in screening for and follow-up of cervical cytologic abnormalities: A systematic review. Ann Intern Med 2000;132:810-9.
Fahey MT, Irwig L, Macaskill P. Meta-analysis of Pap test accuracy. Am J Epidemiol 1995;141:680-9.
Eddy DM. Secondary prevention of cancer: An overview. Bull World Health Organ 1986;64:421-9.
Brown AD, Garber AM. Cost-effectiveness of 3 methods to enhance the sensitivity of Papanicolaou testing. JAMA 1999;281:347-53.
Denton KJ. Liquid based cytology in cervical cancer screening. BMJ 2007;335:1-2.
Siebers AG, Klinkhamer PJ, Vedder JE, Arbyn M, Bulten J. Causes and relevance of unsatisfactory and satisfactory but limited smears of liquid-based compared with conventional cervical cytology. Arch Pathol Lab Med 2012;136:76-83.
Singh VB, Gupta N, Nijhawan R, Srinivasan R, Suri V, Rajwanshi A, et al.
Liquid-based cytology versus conventional cytology for evaluation of cervical pap smears: Experience from the first 1000 split samples. Indian J Pathol Microbiol 2015;58:17-21.
] [Full text]
Taylor S, Kuhn L, Dupree W, Denny L, De Souza M, Wright TC Jr., et al.
Direct comparison of liquid-based and conventional cytology in a South African screening trial. Int J Cancer 2006;118:957-62.
Sharma J, Toi PCh, Siddaraju N, Sundareshan M, Habeebullah S. A comparative analysis of conventional and SurePath liquid-based cervicovaginal cytology: A study of 140 cases. J Cytol 2016;33:80-4.
] [Full text]
Arbyn M, Bergeron C, Klinkhamer P, Martin-Hirsch P, Siebers AG, Bulten J, et al.
Liquid compared with conventional cervical cytology: A systematic review and meta-analysis. Obstet Gynecol 2008;111:167-77.
Ronco G, Cuzick J, Pierotti P, Cariaggi MP, Dalla Palma P, Naldoni C, et al.
Accuracy of liquid based versus conventional cytology: Overall results of new technologies for cervical cancer screening: Randomised controlled trial. BMJ 2007;335:28.
Strander B, Andersson-Ellström A, Milsom I, Rådberg T, Ryd W. Liquid-based cytology versus conventional Papanicolaou smear in an organized screening program: A prospective randomized study. Cancer 2007;111:285-91.
Cheung AN, Szeto EF, Leung BS, Khoo US, Ng AW. Liquid-based cytology and conventional cervical smears: A comparison study in an Asian screening population. Cancer 2003;99:331-5.
Davey E, d'Assuncao J, Irwig L, Macaskill P, Chan SF, Richards A, et al.
Accuracy of reading liquid based cytology slides using the ThinPrep imager compared with conventional cytology: Prospective study. BMJ 2007;335:31.
Sankaranarayanan R, Nene BM, Shastri SS, Jayant K, Muwonge R, Budukh AM, et al.
HPV screening for cervical cancer in rural India. N Engl J Med 2009;360:1385-94.
[Table 1], [Table 2]