Introduction

Cervical cancer remains one of the leading causes of cancer-related morbidity and mortality among women worldwide, particularly in low- and middle-income countries. According to the Global Cancer Observatory (GLOBOCAN 2020), cervical cancer ranks as the fourth most common cancer in women globally, with an estimated 604,000 new cases and 342,000 deaths annually [1].

Papanicolaou (Pap) smear cytology is a widely accepted and cost-effective screening method for the early detection of precancerous and cancerous lesions of the cervix [2]. Introduced by George Papanicolaou in the 1940s, it has significantly reduced the incidence and mortality of cervical cancer in countries with effective screening programs [3]. Despite its success, Pap smear cytology is not without limitations, as false-negative and false-positive results can occur due to sampling errors, interpretation variability, and lesion characteristics [4].

Correlation with histopathological examination, which is considered the gold standard for diagnosis, is essential for assessing the diagnostic accuracy of Pap smear cytology. Measures such as sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) are crucial in determining the reliability of cytological findings [5]. Additionally, statistical tools like the chi-square test help evaluate the association between cytological and histological results, providing a deeper understanding of the effectiveness of cervical cancer screening programs.

This study aims to evaluate the diagnostic accuracy of Pap smear cytology in comparison with histopathology and to statistically analyze their correlation using chi-square analysis.

Material and Methods

A retrospective analysis of 2746 cervical cytology cases was conducted from year 2019 to 2024. Cases were categorized based on the Bethesda System and histopathological correlation was assessed. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy were calculated. Statistical analysis was performed using SPSS.

Results

Total of 2746 reported pap smear cases were retrieved of which 2369 were NILM, 108 were unsatisfactory and 269 were having epithelial lesions. Histopathology was available in 220 and these cases were evaluated for cyto-histo correlation. Out of 220 cases, 56 were unremarkable on both histopathology and cytological, while 6 cases were reported as NILM on cytology but on histopathology were found to be epithelial lesions.

The 269 cytological cases analysed showed the highest prevalence of ASC-US (n=156), followed by HSIL (n=37), LSIL (n=25), AGC (n=16), SCC (n=13), ASC-H (n=14), and adenocarcinoma (n=08). The age distribution of cases is presented in Table 1.

Among the 158 of 220 cases evaluated for cyto-histo correlation and reported as epithelial lesions on cytology, the distribution was as below:
ASC-US (n=72), HSIL (n=30), LSIL (n=18), AGC (n=09), SCC (n=11), ASC-H (n=12), and adenocarcinoma (n=06).

The histopathological confirmation of cases and concordance rates are shown in Table 2.

The most common age group affected was 25–34 years, accounting for the majority of ASC-US cases. High-grade lesions (HSIL, SCC) were more frequent in women aged 25–44 years, while adenocarcinoma predominantly affected women over 55 years.

HSIL, SCC, and adenocarcinoma had a 100% concordance rate with their histological diagnosis, indicating high reliability of cytology in identifying high-grade lesions and malignancies.

LSIL had an 83.3% concordance rate, with some cases histologically upgraded to CIN1 and 2.

ASC-US showed a 44.4% concordance rate, with 55.6% discordance, as some cases were later diagnosed as CIN2/3 or cervicitis.

Atypical glandular cells (AGC) showed the highest discordance (33.3%), indicating the need for further evaluation through additional diagnostic modalities such as HPV testing or colposcopy.

Our study showed pap smear to have high sensitivity 94.5% and specificity of 50.9%.

The positive predictive value (PPV) was 65.8%, while the negative predictive value (NPV) was 90.3%.

The chi-square test revealed a highly significant association between cytological and histopathological diagnoses (χ² = 87.42, df = 6, p < 0.001).

Subgroup analysis demonstrated particularly strong correlations for high-grade lesions (HSIL/SCC: χ² = 42.36, p < 0.001), while low-grade abnormalities (ASC-US/LSIL: χ² = 15.28, p = 0.002) and glandular lesions (AGC: χ² = 8.91, p = 0.012) showed weaker but still significant associations.

Post-hoc power analysis indicated excellent statistical power (98%) with a large effect size (Cramer's V = 0.63).

The statistical findings of all p-values <0.05 strongly suggest that the diagnostic correlations is observed in our study.

These findings emphasize the Pap smear’s effectiveness as a screening tool due to its high sensitivity and negative predictive value but also point to the importance of additional tests like HPV testing to enhance specificity and minimize unnecessary follow-ups. The results support the value of cytology in identifying cervical abnormalities especially, high-grade lesions while also showing that better diagnostic methods are needed for low-grade and glandular changes, where false positives still occur frequently.

Discussion

Cervical cytological abnormalities vary with age, mirroring the typical progression of HPV infection and cervical neoplastic changes. In this study, the 25–34 year age group showed the highest number of cases, with ASC-US being the most commonly detected abnormality. High-grade lesions such as HSIL and SCC were more frequently found in women aged 45–70 years, whereas adenocarcinoma was primarily seen in women older than 55 years.

Prevalence of Low-Grade Lesions in Younger Women

The predominance of ASC-US in women under 45 years aligns with global screening data, where transient HPV infections and mild dysplasia are more frequent in younger individuals. A study conducted by Wendel et al. [6] reported a higher prevalence of ASC-US in the 25–29 year age group, which aligns with our findings. However, they reported LSIL as most common in the 20–24 year age group, which differs from our study. Furthermore, their data showed HPV positivity in 65% of ASC-US cases and 87% of LSIL cases. This study also emphasizes that beyond the age of 25, the prevalence of high-risk HPV is comparable in both LSIL and ASC-US cases, supporting the rationale for implementing HPV triage testing at a younger age.

Another study, done by Arbyn et al [7] showed the effectiveness of high-risk HPV testing as a triage method for ASCUS and LSIL in women aged 25–34, reporting a 20.7% HR-HPV prevalence in premenopausal women, with the 25–34 age group being a key subset. It also highlights a 28.7% progression rate to high-grade lesions in this range.

High-Grade Lesions in Older Women

In contrast, ASC-H, HSIL, Adenocarcinoma and SCC were more prevalent in women above 45 years, suggesting a higher risk of persistent HPV infection and progression to invasive disease. Studies by Landy et al [8] assesses the diagnostic performance of cervical cytology, specifically high-grade squamous intraepithelial lesion (HSIL) or worse, in women aged ≥70 and a cohort aged 40–69 which is similar to this study and highlighting focus on screening efficacy across different age subgroups. The shift from low-grade to high-grade lesions in this age group emphasizes the need for more aggressive management, including colposcopy and biopsy for HSIL.

Diagnostic Concordance

The ASC-US category exhibited a 44.4% concordance rate, with 55.6% of cases being upgraded to CIN1, CIN2/3 or cervicitis on histology. The main contributors to discordance include reactive changes and cervicitis mimicking dysplasia. This finding is close to study done by Stoler et al [9] in which concordance rate was 43% while with Sankaranarayanan et al. [10] reported 64.5% concordance, and Gupta et al. [11] observed 73% concordance.

Similarly, ASC-H showed 58.3% concordance with 41.7% upgraded to CIN2/3, atrophy, and cervicitis with immature squamous metaplasia. Park et al. [12] reported a comparable concordance of 51.4%.

LSIL showed 83.3% concordance and had cases upgraded to CIN2 and immature squamous metaplasia on histology. In contrast, Sankaranarayanan et al. [10] reported a lower concordance rate of 58%.

HSIL showed 100% concordance in the present study, similar to Gupta et al. [11] who also found 100% concordance. However, a lower concordance of 45.4% was documented by Sankaranarayanan et al. [10]

Squamous Cell Carcinoma demonstrated 100% concordance, consistent with findings by Gupta et al. [11]

The AGC category exhibited the lowest concordance (33.3%), with over half of cases (66.7%) demonstrating benign/reactive histology. A higher concordance of 73% was reported by Sankaranarayanan et al.[10]

Adenocarcinoma showed 100% concordance in the current study, which was also reported in studies by Gupta et al. [11], Farooq et al. [13] and Zamora Guerra et al. [14], reflecting consistent cytohistological agreement.

Study done by Gage et al [15] suggested that Lower concordance rates in ASC-US and AGC categories highlight the limitations of cytology alone in low-grade or ambiguous categories. This suggests that HPV testing, repeat cytology, or biomarkers (like p16/Ki-67) may be necessary adjuncts to improve diagnostic accuracy and reduce false negatives in screening.

This study also emphasized on the limited predictive value of a single negative Pap in certain atypical categories, suggesting that repeat testing or adjunct modalities should be integrated into screening protocols.

Another , Study done by Ronco et al [16] showed that 100% concordance was seen in high-grade lesions thus, it supports the continued use of Pap cytology as a highly specific and reliable tool for detecting clinically significant precancerous and cancerous cervical lesions. This ensures timely colposcopic referral and treatment, potentially preventing progression to invasive cancer.

Confounding Lesions Leading to Cytology-Histology Incongruity

In our study, discordance in categories like ASC-US, ASC-H, LSIL, and AGC was mainly due to benign mimickers such as reactive changes, immature squamous metaplasia, and atrophy. These conditions can resemble dysplasia on cytology, leading to overinterpretation. Recognizing these mimickers is crucial to reduce false positives and improve cyto-histological correlation.

Statistical Validation of Pap Smear Diagnostic Accuracy

In our study, High-grade lesions such as HSIL, SCC, adenocarcinoma showed true positive rates, whereas low-grade lesions (ASC-US, LSIL, AGC) had higher false-positive rates due to benign mimickers. The statistical findings of all p-values <0.05 strongly suggest that the diagnostic correlations is observed in our study.

The Pap smear demonstrated a high sensitivity of 94.5%, effectively identifying the majority of true precancerous and malignant lesions. However, the specificity was relatively lower at 50.9%, reflecting some benign conditions (e.g., cervicitis, atrophy) which were misclassified as abnormal, particularly in cases diagnosed cytologically as ASC-US (55.6% discordance) and AGC (66.7% discordance).

The positive predictive value (PPV) was 65.8%, suggesting that approximately two-thirds of cytological positives were true malignancies, while the negative predictive value (NPV) was 90.3%, indicating a high reliability in ruling out disease.

These findings are in concordance with a study by Atla et al.[17], who evaluated 356 Pap smears and reported an overall sensitivity of 94.11%, specificity of 64.28%, PPV of 82.75%, NPV of 85%, and a diagnostic accuracy of 83.33%, with a statistically significant concordance rate of 78.2% (p < 0.001).

Similarly, Dhakal et al. [18] analyzed 1,922 Pap smears and correlated 75 with cervical biopsies. Their study reported a sensitivity of 77.8%, specificity of 100%, PPV of 100%, and NPV of 97%, supporting the reliability of Pap smear in detecting cervical lesions, especially in higher-grade abnormalities.

Another study conducted by Agrawal et al. [19] had 108 cases of cervical cytology with corresponding histopathological evaluation. Among these, 99 cases demonstrated concordance between cytological and histopathological findings, while 9 cases showed discordance. The study reported a sensitivity of 50% and a high specificity of 97.87%. The positive predictive value (PPV) was 77.77%, and the negative predictive value (NPV) was 92.92%. Overall, the diagnostic accuracy achieved was 91.66%, highlighting the reliability of cytology in excluding disease, though its sensitivity in detecting all abnormal cases was limited.

Conclusion

Pap smear remains a simple, cost-effective, and valuable tool for early detection of high-grade cervical lesions and malignancies. Despite its limitations in detecting low-grade changes, its high diagnostic accuracy supports its use as a primary screening method. Histopathological confirmation and adjunctive tests like HPV testing are essential for precise diagnosis. Expanding awareness, routine screening, and public health initiatives can play a vital role in reducing the burden of cervical cancer, especially in underserved communities.

Acknowledgement

We thank the Departments of Pathology and Obstetrics & Gynecology for their support, the technical staff for their assistance, and the patients for their participation in this study.

References

1. Sung H, Ferlay J, Siegel RL, et al. Global cancer statistics 2020: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries. CA Cancer J Clin. 2021;71(3):209–49.
2. Arbyn M, Weiderpass E, Bruni L, et al. Estimates of incidence and mortality of cervical cancer in 2018: a worldwide analysis. Lancet Glob Health. 2020;8(2):e191–203.
3. Papanicolaou GN, Traut HF. The diagnostic value of vaginal smears in carcinoma of the uterus. Am J Obstet Gynecol. 1941;42(2):193–206.
4. Nayar R, Wilbur DC. The Pap test and Bethesda 2014. Acta Cytol. 2015;59(2):121–32.
5. Schiffman M, Castle PE, Jeronimo J, et al. Human papillomavirus and cervical cancer. Lancet. 2007;370(9590):890–907.
6. Brismar-Wendel S, Froberg M, Hjerpe A, Andersson S, Johansson B. Age-specific prevalence of HPV genotypes in cervical cytology samples with equivocal or low-grade lesions. Br J Cancer. 2009;101(3):511–7.
7. Arbyn M, Roelens J, Simoens C, Buntinx F, Paraskevaidis E, Martin-Hirsch PP, et al. Human papillomavirus testing versus repeat cytology for triage of minor cytological cervical lesions. Cochrane Database Syst Rev. 2013;(3):CD008054.
8. Landy R, Castanon A, Dudding N, Lim AW, Hollingworth A, Hamilton W, et al. Cervical cytology and the diagnosis of cervical cancer in older women. J Med Screen. 2015;22(4):207–12.
9. Stoler MH, Schiffman M, for the ASCUS-LSIL Triage Study (ALTS) Group. Interobserver reproducibility of cervical cytologic and histologic interpretations: realistic estimates from the ASCUS-LSIL Triage Study. JAMA. 2001;285(11):1500–5.
10. Sankaranarayanan R, Nene BM, Shastri SS, et al. Accuracy of conventional cytology: results from a multicentre screening study in India. J Med Screen. 2004;11(2):77–84.
11. Gupta R, Hariprasad R, Dhanasekaran K, et al. Reappraisal of cytology-histology correlation in cervical cytology based on the recent American Society of Cytopathology guidelines (2017) at a cancer research centre. Cytopathology. 2020;31(1):53–8.
12. Park JY, Lee SM, Lee KH, et al. Overall accuracy of cervical cytology and clinicopathological significance of LSIL cells in ASC-H cytology. Cytopathology. 2016;27(6):415–22.
13. Farooq R, Quraishi AUN, Mohammad S. Correlation of cervical pap smears with histopathological diagnosis in cervical lesions. Int J Reprod Contracept Obstet Gynecol. 2021;10(12):4478–81.
14. Guerra ZYU, Ramírez CS. Cytological diagnosis of cervical adenocarcinoma and cytohistological agreement at General Hospital of Mexico “Dr. Eduardo Liceaga”. Rev Med Hosp Gen Mex. 2018;81(1):1–6.
15. Gage JC, Schiffman M, Katki HA et al. Reassurance against future risk of precancer and cancer conferred by a negative human papillomavirus test. J Natl Cancer Inst. 2014;106(8):dju153.
16. Ronco G, Dillner J, Elfström KM et al. Efficacy of HPV-based screening for prevention of invasive cervical cancer: follow-up of four European randomised controlled trials. Lancet. 2014;383(9916):524–32.
17. Atla BL, Uma P, Shamili M, Kumar SS. Cytological patterns of cervical pap smears with histopathological correlation. Int J Res Med Sci. 2015;3(8):1911–6.
18. Dhakal R, Makaju R, Sharma S, Bhandari S, Shrestha S, Bastakoti R. Correlation of cervical pap smear with biopsy in the lesion of cervix. Kathmandu Univ Med J. 2016;55(3):254–7.
19. Agrawal S, Agrawal S, Gupta P. Study of cervical cytology in pap smears in a tertiary care hospital of North Maharashtra. Int J Reprod Contracept Obstet Gynecol. 2023;12(7):2185–92.