Common causes for unsatisfactory Pap tests in a high-risk population: insights into a yet unresolved problem in gynecologic cytology

Introduction

Although the rates are generally low (0.2%-10%), unsatisfactory Papanicolaou (Pap) tests are associated with an increased risk of epithelial lesions on subsequent follow-up. Therefore, some studies have recommended extra laboratory processing, resampling of patients, and more recently, human papillomavirus testing.

Materials and methods

Consecutive cases signed out as unsatisfactory for evaluation (UE) were identified from January 1, 2008 to December 31, 2010 in the cytology laboratory at Houston Methodist Hospital. Patient’s demographics, relevant prior clinical history, type of Pap test, reasons for UE diagnosis, and cytology or histology follow-up were obtained from the pathology database.

Results

Among 56,563 total Pap tests, 276 were signed out as UE (0.47%). Nearly half of these patients were older than 50 years (15 to 88 years). The majority (85%) of patients over 50 years old had a history of prior gynecologic cancer. Low squamous cellularity was the most common cause of UE in all age groups. Follow-up abnormalities were identified in 21 of 73 patients (29%).

Conclusions

Low squamous cellularity was the most common cause of UE and was often seen in women older than 50 years of age. The significant risk associated with UE emphasizes the importance of appropriate follow-up on these patients.

Introduction

The rate of unsatisfactory Papanicolaou (Pap) tests has been reportedly around 1.1% of cervicovaginal cytology specimens, according to the latest College of American Pathologists survey.¹ Cases assigned to this category have been associated with an increased risk of epithelial lesions on subsequent follow-up.2, 3 Therefore, additional laboratory processing4, 5, 6 or resampling of patients7, 8 has been proposed. More recently, human papillomavirus (HPV) testing has been proposed for triaging the specimens with unsatisfactory cytology.7, 9 This becomes a relevant issue when we consider the anticipated increase in costs for both the patient and the laboratory.

Since the implementation of adequacy criteria from the Bethesda System for reporting cervical cytology¹⁰ in conjunction with the introduction of liquid-based cytology (LBC) in our laboratory in 1998, we have noticed a reduction in unsatisfactory rates of Pap tests. The impact of LBC in reducing unsatisfactory Pap tests has been well recognized by many investigators.11, 12, 13, 14 However, complete eradication of this problem has not been accomplished to date. The current study aimed to investigate the prevalence, common causes, and clinical features associated with unsatisfactory Pap tests in our patient population following the implementation of LBC and the Bethesda Reporting System.