Silent High Grade Cervical Intraepithelial Neoplasia Diagnosis of Atypical Smear between Conventional and Liquid Based Papanicolaou Smear in Suburban Area of Thailand

Cervical cancer screening test is an important procedure to detect precancerous and cervical cancerous lesions. Cervical cancer screening can reduce the incidence of invasive cervical cancer. In Thailand, the main method of cervical cancer screening is conventional Papanicolaou test (CPP) due to its low cost which is fully supported by government health care program. Liquid based Papanicolaou test (LBP), human papillomavirus (HPV) test, co-testing (LBP and HPV test) and HPV genotyping have been Abstract

Introduction management in women with ASC-US on cytology is either a repeat cytology at one year or an immediate HPV testing (reflex test). Colposcopy was recommended in ASC-US cases with positive result of high-risk HPV test. From Heng's and Lertvutivivat's works [7][8], the ratio of prevalence of CIN 2/3 and cancer in ASC-US cytology were 16.6 to 3.5 and 0 to 1.8 percent, reported from CPP and LBP, respectively.
The objective of this study was to evaluate the prevalence of silent high grade cervical intraepithelial neoplasia (CIN 2/3 and cancer) in ASC-US cytology result between CPP and LBP methods used in our hospital to suggest the proper management based on our patient population.

Materials and Methods
The retrospective study was approved by the institutional review board, Bhumibol Adulyadej Hospital, Bangkok, Thailand (IRB: 20/61). Data were reviewed from medical records stored in a computerized program. Data from all patients with CPP and LBP in 6 years period between January 2011and December 2016 were collected. Inclusion criteria were women who had cervical cytology result with ASC-US cytology. Exclusion criteria were women with pregnancy, post hysterectomy and known history of pre-invasive or invasive cervical lesion or other gynecologic cancers. Data collected from medical records included age, type of cervical cancer test, cytology results, colposcopic examination, and histopathological reports. Demographic characteristic consisted of age, menstrual status, Pap proposal, contraception, history of the sexually transmitted disease (STD) including human immunodeficiency virus (HIV), history of multiple partners, occupation, smoking, and alcohol consumption. Management of ASC-US cytology was followed by the previous ASCCP guideline by either a repeated cervical cytology testing in 6 months or a colposcopic directed biopsy (immediate colposcopy or positive high-risk HPV test). Descriptive statistics were used to analyze patient demographic data. Continuous data were expressed as the mean and standard deviation (SD). Categorized data were expressed as number and percentage. Pearson Chi-square and Fisher's exact test were used in data analysis when appropriate. The p value of 0.05 or less was considered to be statistically significant. The analysis was performed using the SPSS statistic version 18 (SPSS, Chicago, IL, USA).

Results
This study was conducted in the Headquarter of the Royal Thai Air Force Hospital. Around one-fifth of the population in this study were air force personals and their families. The remaining patients were people who lived and worked in the nearby area around this air force base. Patients also came from a wholesale market, Talad Si Mum Muang, located in a nearby area.
A total of 28,564 medical records were reviewed during the study period. There are 22,552 and 6,012 cases in CPP and LBP groups, respectively. A total of 990 atypical cervical cytology cases were enrolled. Only 644 cases of atypical smears cases were ASC-US reports. Other atypical squamous cells smears not included were high grade squamous intraepithelial lesion (ASC-H), atypical glandular cells (AGC) and atypical glandular cells favor neoplasia (AGCFN) at 98, 223 and 25 cases respectively ( Figure 1). Table 1 showed the demographic characteristic of participants in this study. There are 23,009 and 644 cases in NILM and ASC-US groups, respectively. The participants in ASC-US group had a lower age than the control group with statistically significant. The mean age of women with ASC-US versus NILM in cytology were 41.03 and 46.28 years, respectively. The clients in ASC-US also had significantly higher percentage of the multiple sexual partners and pre-menopausal status than the control group. Three-quarters of ASC-US cases (460/644) were in premenopausal status.
The histopathological reports of atypical cervical cytology were represented in Table 2. The prevalence of less than or equal to CIN 1 and CIN 2 or higher in ASC-US reports was 90.5/88.1 and 9.5/11.9 percent in CPP and LBP groups, respectively. Ten percent (23/248) of atypical smear containing glandular cells types were cancerous. One-quarter of them was endometrial cancer.

Discussion
ASC-US is the most common cytological abnormality in cervical cytology. It carried the lowest risk of CIN 3 or cancer because one third to two third was not HPV associated [9]. From ASCCP guideline, there was three tier of management in the women who had ASC-US    year or an HPV testing. For women with HPV-positive ASC-US, either from reflex HPV testing or co-testing, a colposcopy is recommended. Repeat co-testing at one year was recommended in women with HPV-negative ASC-US, whether it was from reflex HPV testing or co-testing. Immediate colposcopy was not further recommended because ASC-US had less than 3 percent CIN 3 or cancer development in 5 year period [9]. In the present study, the prevalence of CIN 2/3 and cancer in ASC-US cytology were 9.5 and 11.9% from CPP and LBP group, respectively. From the previous investigations, the prevalence of CIN 2/3 and cancer were between 5.3-26.8 percent [7-8-10-12]. The result of our study supported the former studies. In this study, the prevalence of CIN 2+ from either CPP or LBP was no statistical difference (p = 0.752).
Colposcopy with direct biopsy is a gold standard method for diagnosis of pre or invasive cervical cancer. During the study period, the management of ASC-US cytology was conducted based on previous ASCCP guideline. The ASC-US cases were undergoing repeat cervical cytology, immediate colposcopy, and colposcopy after the positive result of the high-risk HPV test. In our study, more than half (376/644) of ASC-US cases underwent colposcopic directed biopsy. Most physicians preferred to repeat cytology as a follow-up method due to its economical expense and ease of operation in Thailand. The sensitivity and specificity of CPP and LBP for the detection of CIN 2/3 and cancer were approximately 55.2 to 57.1 and 96.7 to 97.0 percent, respectively [13]. Our study revealed 80% of participants received CPP for cervical cancer screening. HPV testing had higher accuracy than repeat cytology method. It led to faster and more complete diagnosis of pre and invasive cervical diseases. Cuzick's work showed that in women with ASC-US cytology, time to CIN3+ detection was much shorter in women with HPV testing than without testing [14].
Nowadays HPV testing has not been performed as a primary screening test in government hospitals. Limitation of its usage was its higher expense, and a copayment was needed in a government health setting. From another Thai hospital study, women with ASC-US cytology had a 40 percent risk of HPV [8]. In the present study, four percent (26/644) of the patient with ASC-US in cytology underwent HPV testing. Half of HR-HPV test in ASC-US cases had the positive result. All cases of ASC-US with positive or negative HR-HPV testing had no CIN2+.
In this study, the finding suggested all patients with ASC-US cytology from both methods for cervical screening (CPP vs LBP) should undergo immediate colposcopic directed biopsy. This suggestion was not following the latest ASCCP guideline because our finding showed a high prevalence of high grade cervical intraepithelial lesions (CIN 2+) (9.5 to 11.9 %). Our result is similar to previous works done in Thailand [8-15-16]. Our data showed that the silent of CIN2+ in ASC-US group was as high as LSIL group. The suggestion from this study did not follow the latest guideline of ASCCP. The ASCCP guideline was created on the data of the populations whose had the lower incidence of cervical cancer than the present study population.
In this study, ten percent (23/248) of atypical smear containing glandular cells types were cancerous. One-quarter of them was endometrial cancer. From the previous study, AGC in women at age of 35 or older usually contained cancer around 3% compared to 10 % in this study [17]. This report showed the higher prevalence of cancer. This study supported the recommendation of  colposcopy and endometrial biopsy followed by ASCCP guideline.
In conclusion, the silent high-grade CIN in ASC-US cases was higher than the data of the ASCCP guideline. Based on our patient population, we recommended colposcopy in the women who had cervical cytology report of ASC-US without HPV testing result and AGC. The suggestion might be applied to the referral center that the incidence of silent high-grade CIN was high.