Cell block preparation in urine cytology: examination of utility and workflow in an academic practice

Urine cytology is a common non-invasive test to screen for urothelial carcinoma. Urine cell blocks may sometimes be prepared as a diagnostic aid (eg, to characterize architecture or perform immunohistochemistry). The aim of this study was to determine whether routinely preparing cell blocks on urine specimens improves diagnostic sensitivity.

Three time periods were compared: time period 1 (prior to November 2009; 1437 consecutive selected cases), when cell blocks were rarely prepared; period 2 (November 2009 to May 2010; 1230 selected cases), when cell blocks were prepared on all cases; and period 3 (after May 2010; 1499 consecutive selected cases), when cell blocks were made only when indicated (for samples with substantial cellular pellets or when requested by a pathologist).

Patient demographics and the type of specimens received were relatively similar during the 3 time periods. Increased preparation of cell blocks was not accompanied by a notable improvement in specimen adequacy rate, given that <1%, 2%, and 1% of samples were unsatisfactory for the 3 periods. Only the proportion of atypical cases differed during the time periods, being highest in period 1 (23%), but lower in periods 2 and 3. Turnaround time was fastest for period 1 (mean: 47 hours, median: 33 hours), and slower for period 2 and period 3.

These data show that routinely preparing cell blocks for urine samples did not improve our laboratory's specimen adequacy rate. Nonetheless, cell block preparation on urine samples did help lower the proportion of atypical diagnoses, when routinely or selectively prepared. Because preparation of cell blocks on all urine cases can be costly and only provides minimal added clinical benefit, our recommendation is to rather judiciously utilize cell blocks when screening urine cytology samples.