A prolonged microscopic observation improves detection of underpopulated cells in peripheral blood smears.

We evaluated an extended time in the microscopic review in samples in which the potential clinical information could be increased with respect to those that could be achieved with the usual laboratory methodologies. We used samples containing nucleated red blood cells in a small amount and cytopenic samples. For these purposes for each peripheral blood smear, the timing of eye-count differential was increased up to 20 min, regardless of the final number of cells which could be counted. In addition, an automated system for digital analysis of peripheral blood smears was employed and the number of cells counted was brought up to 1000 leukocytes. In both manual and automatic light microscopy extended observation, we obtained more diagnostic information in respect to those with routine or standard methods. Both automated and manual increase systems of the timing for microscopic review are useful tools to find diagnostic information that otherwise would be lost using normal and standard procedures. So, these methods should be used especially when there is a higher pre-test probability for discovery of pathological cells.