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.