Inaccurate Cell Count Leading to Protocol Mismatch

Symptom

Unexpectedly high or low DNA yield that does not correlate with estimated cell count. Certain cultured cells appear clumped making accurate counting difficult.

1. 1 Cultured cells (e.g., HEK293) tend to clump, making hemocytometer counting difficult
2. 2 Cell clumping usually leads to underestimation of cell count
3. 3 Underestimated count leads to using standard protocol when low-input protocol needed
4. 4 Dilute samples incorrectly estimated above 5 × 10⁵, causing reduced prep efficiency with standard protocol

1. 1 For clumping cells: use trypan blue and thorough mixing before counting to disaggregate cells
2. 2 Take multiple counts from different aliquots to verify cell concentration
3. 3 If yield is unexpectedly high with assumed low count: actual count was higher, use standard protocol next time
4. 4 If yield is unexpectedly low with assumed high count: actual count was ≤ 5 × 10⁵, use low-input protocol (3X reduced volumes)
5. 5 Consider automated cell counting or flow cytometry for difficult-to-count cell types