N. Gupta, D. John, N. Dudding, J. Crossley and J. H. F. Smith
Factors contributing to false-negative and potential false-negative cytology reports in SurePath™liquid-based cervical cytology
Objectives: The characteristics of false-negative conventional cervical cytology smears have been well documented, but there is limited literature available for liquid-based cytology (LBC), especially SurePath™ samples. We aimed to assess the characteristics of false-negative SurePath LBC samples.
Methods: Over a period of 5 years, an audit of false-negative reports in SurePath cervical cytology was undertaken. In a workload of 183, 112 samples, 481 (0.3%) false negatives were identified using two routes: those detected by routine laboratory internal quality control (rapid pre-screening) (n = 463) and those reported as normal (true false negatives) with concurrent high-grade cervical histology (n = 18). Ninety-five false-negative cases with a subsequent biopsy reported as at least cervical intraepithelial neoplasia grade 2 (CIN2+) were reviewed for a number of different cytomorphological features.
Results: Of 95 samples with subsequent CIN2+, 30.5% predominately contained microbiopsies/hyperchromatic crowded cell groups (HCGs), 27.3% sparse dyskarytotic cells, 4.2% pale cell dyskaryosis, 6.3% small dyskaryotic cells; 3.2% were misinterpreted cells, 8.4% contained other distracting cells, 7.4% were low contrast, 5.3% were unexplained and 7.4% were true negatives. The mean number of microbiopsies/HCGs in that category was 4.6. The mean number of abnormal cells in the sparse dyskaryotic cell category was 13.8.
Conclusions: Microbiopsies/HCGs were the commonest reason for false negatives. They were usually present in sufficient numbers to be detected but interpretation could be problematic. Dispersed single abnormal cells were usually not identified because of their scarcity or the presence of distracters.