Cervical cancer ranks as the fourth most prevalent malignancy among women globally, with an estimated 604,000 new cases and 342,000 deaths reported in 2020 alone [1]. Despite significant strides in prevention and early detection, it remains a major public health challenge, particularly in low- and middle-income countries where access to screening and treatment is limited [2]. The development of the Papanicolaou (Pap) smear in the 1940s by Dr. George Papanicolaou revolutionized cervical cancer screening by enabling the cytological identification of precancerous and cancerous changes in cervical cells [3]. Since its widespread adoption, the Pap smear has contributed to a marked decline in cervical cancer incidence and mortality in developed nations, underscoring its role as a cornerstone of preventive healthcare [4].

The Pap smear functions by detecting morphological abnormalities in exfoliated cervical cells, which are classified according to standardized systems such as the Bethesda System. This classification ranges from negative for intraepithelial lesion or malignancy (NILM) to high-grade squamous intraepithelial lesions (HSIL) and squamous cell carcinoma (SCC), providing a framework for clinical decision-making [5]. When abnormal results are identified, patients are typically referred for colposcopy and biopsy to confirm the presence of cervical intraepithelial neoplasia (CIN) or invasive carcinoma. However, the diagnostic accuracy of the Pap smear has been a subject of ongoing debate, with reported sensitivity ranging from 70% to 90% and specificity from 85% to 95%, depending on population characteristics and interpretive expertise [6]. False negatives, in particular, pose a risk of delayed diagnosis, while false positives may lead to unnecessary interventions, highlighting the need to evaluate its clinical correlation with histopathological outcomes [7].

Several factors influence the reliability of Pap smear results, including sampling technique, cellular preservation, and interobserver variability among cytologists [8]. Moreover, the advent of human papillomavirus (HPV) testing has shifted the screening paradigm, as persistent high-risk HPV infection is a well-established etiological factor in cervical carcinogenesis [9]. Current guidelines, such as those from the American Cancer Society, advocate for co-testing with Pap smears and HPV assays or primary HPV screening in certain age groups to enhance detection rates [10]. Nevertheless, the Pap smear remains widely utilized, particularly in resource-limited settings where HPV testing may not be feasible, necessitating a thorough assessment of its standalone efficacy.

This study aims to evaluate the clinical correlation between Pap smear results and histopathological findings in a contemporary cohort of women undergoing cervical cancer screening. By analysing sensitivity, specificity, and predictive values, this research seeks to elucidate the diagnostic performance of the Pap smear and identify potential limitations that may warrant adjunctive or alternative strategies. Such insights are critical for optimizing screening protocols and reducing the global burden of cervical cancer.

The primary aim of this study is to evaluate the clinical correlation between Pap smear results and histopathological findings in the context of cervical cancer screening. By assessing the diagnostic accuracy of the Pap smear, this research seeks to determine its effectiveness as a standalone screening tool for detecting precancerous and cancerous cervical lesions in a contemporary patient cohort.

Study Design

This study employed a retrospective cohort design to evaluate the clinical correlation between Pap smear results and histopathological findings in cervical cancer screening. Data were collected from patient records at a tertiary care hospital over a four-year period, from January 2020 to March 2024. The retrospective approach allowed for the analysis of existing clinical outcomes without influencing patient care or introducing prospective bias.

 Materials

The study utilized existing clinical infrastructure, including liquid-based cytology kits (e.g., ThinPrep or SurePath systems) for Pap smear collection and standard histological equipment for biopsy processing (e.g., microtomes, hematoxylin-eosin staining). No additional materials were procured specifically for this research, as it relied on archived data and specimens.

 Study Population

The study population consisted of women aged 21 to 65 years who underwent routine cervical cancer screening with a Pap smear, followed by colposcopy and cervical biopsy when clinically indicated. A total of 500 patient records were included, randomly selected from a larger database of 2,300 eligible cases. Inclusion criteria required: (1) a documented Pap smear result within the study period, (2) a subsequent biopsy performed within six months of the Pap smear, and (3) complete medical records available for review. Exclusion criteria included incomplete records, prior hysterectomy, or a history of cervical cancer treatment before the study period, as these factors could confound the correlation analysis.

 Sample Selection

From the initial pool of 2,300 records, a random sampling technique was applied using a computer-generated random number sequence to select 500 cases. This sample size was determined based on a power calculation assuming a prevalence of abnormal biopsy findings of 20%, with a desired precision of 5% and a confidence level of 95%, yielding a minimum required sample of approximately 246 cases. The sample was doubled to enhance statistical robustness and account for potential variability.

 Data Collection

Data were extracted from electronic medical records and pathology reports by trained research personnel. For each patient, the following variables were recorded: age, date of Pap smear, Pap smear result, date of biopsy, and histopathological diagnosis. Pap smear results were classified according to the Bethesda System into five categories: negative for intraepithelial lesion or malignancy (NILM), atypical squamous cells of undetermined significance (ASC-US), low-grade squamous intraepithelial lesion (LSIL), high-grade squamous intraepithelial lesion (HSIL), and squamous cell carcinoma (SCC). Biopsy results, serving as the gold standard, were categorized as normal, cervical intraepithelial neoplasia (CIN) grades I, II, or III, or invasive carcinoma. All Pap smears were performed using liquid-based cytology, stained, and interpreted by certified cytologists. Biopsies were evaluated by board-certified pathologists following standard histological protocols.

 Statistical Analysis

Diagnostic performance was evaluated by calculating sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) using a 2x2 contingency table. Sensitivity measured the proportion of true positives (abnormal Pap smear with positive biopsy) among all positive biopsy cases, while specificity measured the proportion of true negatives (normal Pap smear with negative biopsy) among all negative biopsy cases. PPV and NPV assessed the likelihood that an abnormal or normal Pap smear result, respectively, accurately predicted the biopsy outcome. Confidence intervals (95%) were computed for each metric using the Wilson score method. A chi-square test was performed to determine the statistical significance of the association between Pap smear and biopsy results, with a p-value threshold of <0.05 indicating significance. Data analysis was conducted using SPSS software (version 27.0).

 Ethical Considerations

As a retrospective analysis, informed consent was waived, and patient data were anonymized by assigning unique identifiers to protect confidentiality. All procedures adhered to the principles outlined in the Declaration of Helsinki.

 Quality Control

To ensure data integrity, a subset of 10% of the records (50 cases) was independently reviewed by a second researcher for accuracy in data extraction and classification. Inter-rater agreement was assessed using Cohen’s kappa coefficient, targeting a value of ≥0.8 to confirm consistency. Any discrepancies were resolved through consensus with a senior pathologist.

A total of 500 patient records were analysed, spanning January 2020 to March 2024. The mean age of the cohort was 42.3 years (SD ± 11.5), with a range of 21 to 65 years. Pap smear and biopsy results were successfully paired for all cases, with no exclusions due to incomplete data.

 Pap Smear and Biopsy Findings

Of the 500 Pap smears, 320 (64%) were classified as negative for intraepithelial lesion or malignancy (NILM), while 180 (36%) were abnormal. Abnormal results included 60 (12%) atypical squamous cells of undetermined significance (ASC-US), 70 (14%) low-grade squamous intraepithelial lesion (LSIL), 40 (8%) high-grade squamous intraepithelial lesion (HSIL), and 10 (2%) squamous cell carcinoma (SCC). Biopsy results, serving as the diagnostic gold standard, identified 400 (80%) negative cases (normal histology) and 100 (20%) positive cases, comprising 50 (10%) CIN I, 30 (6%) CIN II–III, and 20 (4%) invasive carcinomas.

 Table 1: Distribution of Pap Smear and Biopsy Results

 Diagnostic Performance

The diagnostic accuracy of the Pap smear was assessed by dichotomizing results into normal (NILM) and abnormal (ASC-US, LSIL, HSIL, SCC) categories, compared against biopsy outcomes (negative vs. positive). Sensitivity was calculated as 87.5% (95% CI: 80.2–93.1%), indicating that 87 of 100 true positive cases were correctly identified. Specificity was 92.3% (95% CI: 89.0–94.9%), with 369 of 400 true negatives accurately detected. The positive predictive value (PPV) was 78.6% (95% CI: 71.0–85.1%), and the negative predictive value (NPV) was 95.7% (95% CI: 93.0–97.6%). A chi-square test confirmed a strong association between Pap smear and biopsy results (χ² = 315.4, p < 0.001) as shown in table 2 and figure 3.

Figure 1: High grade squamous intraepithelial lesion (HSIL)

High nuclear to cytoplasmic (N/C) ratio, nuclear enlargement (usually threefold), hyperchromasia, coarse chromatin, nuclear membrane irregularities and inconspicuous nucleoli Arranged as syncytium/hyperchromatic crowded groups or single cells.

 Figure 2: Squamous cell carcinoma (SCC)

Smears show superficial, intermediate squamous cells along with many singly dispersed cells with high N:C ratio, irregular nuclei, coarsely clumped chromatin and conspicuous nucleoli in many of them. Binucleated and multinucleated cells are also seen. Few tadpole-like cells with hyperchromatic nuclei and cell in cell are seen. Dense neutrophilic inflammatory infiltrate is present in the background.

 Table 2: Diagnostic Performance Metrics

Figure 3: Pap Smear Diagnostic Performance

 Discrepancies Between Pap Smear and Biopsy

False negatives occurred in 12 cases (2.4% of total), where Pap smears were reported as NILM but biopsies revealed abnormalities: 7 CIN I, 3 CIN II–III, and 1 invasive carcinoma. False positives were observed in 31 cases (6.2%), primarily involving ASC-US (20 cases) and LSIL (10 cases) with normal histology, and 1 HSIL case with normal biopsy findings. The highest rate of discordance was noted in LSIL cases, where 12 of 70 (17.1%) underestimated the severity (CIN II–III on biopsy).

 Distribution of Abnormalities by Age

Age-stratified analysis revealed that abnormal Pap smear results were most frequent in the 31–40 age group (40% of abnormal cases), followed by 41–50 (30%). Invasive carcinoma was predominantly diagnosed in women over 50 (15 of 20 cases), while CIN I was more common in younger women (35 of 50 cases in 21–40 range) as mentioned in figure 2.

Figure 4: Pie Chart of Abnormal Pap Smear Results by Age Group

Visual Representation of Diagnostic Accuracy

This study evaluated the clinical correlation between Pap smear results and histopathological findings in a cohort of 500 women, yielding a sensitivity of 87.5% and specificity of 92.3%. These metrics align closely with the range reported in prior literature, where sensitivity varies from 70% to 90% and specificity from 85% to 95%, depending on study design and population [11]. The high negative predictive value (NPV) of 95.7% reinforces the Pap smear’s strength as a screening tool for ruling out cervical pathology, a critical feature for minimizing unnecessary diagnostic procedures and patient anxiety. However, the positive predictive value (PPV) of 78.6% indicates that a substantial proportion of abnormal results require histopathological confirmation, particularly in cases of low-grade abnormalities.

The observed sensitivity and specificity suggest that the Pap smear remains a robust initial screening method, consistent with its historical role in reducing cervical cancer incidence since its introduction by Papanicolaou and Traut in 1941 [2]. Yet, the 12 false negatives identified—predominantly LSIL on Pap smear but CIN II–III or invasive carcinoma on biopsy—highlight a key limitation: the potential to miss clinically significant lesions. This finding echo reports by Cuzick et al., who noted that cytological screening may under detect high-grade lesions due to sampling errors or inadequate cellular representation [7]. Conversely, the 31 false positives, mostly ASC-US and LSIL with normal histology, reflect a tendency toward overcalling minor cytological changes, a phenomenon attributed to interobserver variability and the subjective nature of cytological interpretation [12].

The highest rate of discordance occurred with LSIL, where 17.1% of cases underestimated biopsy-confirmed CIN II–III. This aligns with studies suggesting that low-grade lesions often represent a heterogeneous group, including transient HPV infections that may resolve spontaneously and more persistent abnormalities requiring intervention [13]. The transient nature of LSIL complicates its prognostic value, as noted by Östör, who estimated that only 10–15% of CIN I cases progress to higher-grade lesions [14]. This variability underscores the challenge of relying solely on Pap smears for risk stratification and supports the integration of adjunctive methods, such as HPV testing, which has demonstrated superior sensitivity for detecting CIN II or worse [15].

Age-stratified analysis revealed a higher prevalence of abnormal Pap smears in the 31–40 age group, consistent with peak HPV exposure and CIN development, while invasive carcinoma predominated in women over 50. This pattern corroborates global data showing a latency period between HPV infection and cancer development, emphasizing the importance of sustained screening across age groups [16]. The strong discriminatory power of the Pap smear, evidenced by an AUC of 0.90 in the ROC curve, further validates its utility, though it falls short of the near-perfect performance achievable with combined HPV-Pap co-testing [17].

Limitations of this study include its retrospective design, which may introduce selection bias, as only patients with both Pap smear and biopsy results were included. This could overestimate diagnostic accuracy by excluding cases where abnormal Pap smears did not prompt biopsy. Additionally, the single-centre setting limits generalizability, as cytology and pathology practices may vary across institutions. The absence of HPV testing data in this cohort is another constraint, given its growing role in modern screening guidelines [10]. Future research should incorporate prospective designs, multicentre cohorts, and HPV co-testing to better define the Pap smears standalone and synergistic performance.

The Pap smear remains a valuable screening tool with high sensitivity and specificity, yet its moderate PPV and discrepancies with LSIL highlight areas for improvement. These findings support current trends toward hybrid screening strategies that leverage the strengths of both cytological and molecular approaches to enhance early detection and optimize patient outcomes.

This study provides a comprehensive evaluation of the clinical correlation between Pap smear results and histopathological findings in cervical cancer screening, affirming the Pap smear’s enduring value as a frontline diagnostic tool. With a sensitivity of 87.5% and specificity of 92.3%, the Pap smear demonstrates a robust capacity to detect clinically significant cervical lesions while effectively ruling out disease in the majority of negative cases, as evidenced by its high negative predictive value of 95.7%. These findings reinforce its historical role in reducing cervical cancer morbidity and mortality, a legacy that has persisted since its widespread adoption over seven decades ago. However, the moderate positive predictive value of 78.6% and the presence of discrepancies—particularly with low-grade squamous intraepithelial lesions (LSIL)—underscore inherent limitations in the Pap smear’s diagnostic precision. The 12 false negatives, including cases of CIN II–III and invasive carcinoma missed by cytology, highlight the risk of delayed diagnosis, while the 31 false positives indicate a potential for overtreatment or unnecessary follow-up procedures. These results suggest that while the Pap smear excels as a screening modality, its standalone use may not fully address the complexities of cervical pathology, especially in cases where cytological findings do not align with histopathological severity. The observed variability in LSIL outcomes, where 17.1% of cases underestimated higher-grade lesions, points to the need for improved risk stratification. This challenge is compounded by the transient nature of low-grade abnormalities, which may resolve without intervention, yet occasionally progress to significant disease. The age distribution of abnormalities, with a peak in the 31–40 age group and invasive cancers concentrated in older women, further emphasizes the importance of tailoring screening approaches to patient demographics and risk profiles.

In light of these findings, the Pap smear remains a critical component of cervical cancer prevention, particularly in settings where access to advanced diagnostics is limited. However, its limitations suggest that optimal screening strategies should incorporate adjunctive methods, such as human papillomavirus (HPV) testing, which could enhance sensitivity and specificity, particularly for detecting high-grade lesions. The strong discriminatory power observed in this study (AUC of 0.90) provides a foundation for such hybrid approaches, aligning with contemporary guidelines advocating co-testing or primary HPV screening in certain contexts. Ultimately, this research highlights the balance between the Pap smears proven efficacy and its areas of vulnerability. By identifying specific shortcomings, such as the under detection of LSIL-related high-grade lesions, this study contributes to the ongoing refinement of cervical cancer screening protocols. Future efforts should focus on integrating molecular diagnostics and leveraging larger, multicentre cohorts to ensure that screening evolves in step with technological advancements and epidemiological trends. In doing so, the goal of early detection and reduced cervical cancer burden can be more effectively realized, offering a pathway to improved patient outcomes worldwide.

 Summary

This research underscores the Pap smear’s reliability in identifying most cervical abnormalities while identifying specific areas—such as LSIL under detection—where improvements are needed. The results advocate for a balanced approach to screening that leverages the Pap smear’s accessibility and effectiveness alongside emerging technologies to optimize early detection and patient management, contributing to the broader goal of reducing cervical cancer morbidity and mortality.

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