Accurate assessment of cell density in low cellular liquid-based cervical cytology
Siebers AG et al. – ThinPrep slides reported as unsatisfactory or SBLB were shown to contain fewer than 20000 squamous cells. The most accurate protocol for estimating the cellularity of these slides was cell counting in five non–adjacent microscope fields along the horizontal axis and five along the vertical axis of the slide with a×10 objective and applying a correction factor of 1.24× to correct for underestimation of the true cellularity.Methods
- A series of 60 ThinPrep cases representing the full spectrum of adequate, ‘satisfactory but limited by’ (SBLB) and unsatisfactory reports were included.
- Two cell-counting protocols with three different magnifications, using ×10, ×20 and ×40 objectives, were evaluated and related to the true cellularity, together with a reassessment of the degree of adequacy originally reported.
- The cell-counting protocol that showed the highest correlation coefficient was considered the most accurate.
- Based on seven (re)assessments a majority score for adequacy was established.
- There were 42 cases with a majority score ‘unsatisfactory’ or ‘SBLB’ (low cellularity) of which 41 contained fewer than 20 000 squamous cells; and 18 cases with a majority score ‘satisfactory’ of which one had fewer than 20 000 cells.
- The cell-counting protocol that showed the significantly highest correlation with the reference standard was the Stichting Kwaliteitsbewaking Medische Laboratoriumdiagnostiek (SKML) protocol with a ×10 objective.