Guides · Lab and field counts
Laboratory and field counting guides
Manual counts still matter wherever an analyser flags a sample, a teaching lab has no machine, or the thing being counted is a plant in a field. These guides set out the counting method, the formula that turns a tally into a result, and the reference ranges from the published sources they cite. They are for study and checking work, not for diagnosis.
All lab and field counts guides
How to make a blood smear, and how to fix a bad oneDrop, angle and speed for a wedge smear, why sources give 30, 35-45 or 45 degrees, the check before staining, and each common fault traced to its cause.Published · 15 min read
McMaster faecal egg count, and where the factor comes fromThe McMaster factor derived from grams, millilitres and chambers, six published recipes compared, worked counts, and the chance that a zero count misses eggs.Published · 15 min read
Manual reticulocyte count with a Miller discThe Miller disc formula worked through, why 111 small-square cells stand for 1,000, the reticle-ratio check, counting error, and the corrected count and RPI from Hillman's 1969 data.Published · 15 min read
Platelet estimate from a blood smearThe 10-field method worked through, why the multiplier depends on your microscope's field number, the red cell ratio method that does not, and how to derive your own factor.Published · 14 min read
Mark and recapture: Lincoln-Petersen, Chapman and the confidence intervalBoth estimators worked through, which confidence interval fits your counts, the five assumptions, and what a handful of recaptures does to the answer.Published · 15 min read
How to identify white blood cells on a smear, and the look-alikesThe five white cells by size, nucleus and granules, the look-alikes that cause most misclassification, and what ICSH says each one counts as in a differential.Published · 19 min read
Quadrat sampling, from the count to the population estimateThe edge rule the field manuals recommend, a population estimate worked with its error, the sample-size formula behind "how many quadrats", and cover scales.Published · 17 min read
How to count cells with a hemocytometerWhy the factor is 10⁴ for one Neubauer square and 10³ for ten, the edge rule, trypan blue viability, how many cells to count and the check that two counts agree.Published · 19 min read
Band or segmented neutrophil, and what a left shift meansThe filament rule and the one-third rule give different band counts on the same smear. Both rules, worked examples, left shift, and the studies measuring how far observers disagree.Updated · 23 min read
How to calculate the absolute neutrophil count (ANC)The formula with bands, the two units and the ×10 shortcut, five worked examples, the absolute lymphocyte count, and why CTCAE grade 4 no longer means below 500.Updated · 21 min read
WBC differential normal ranges, in percentages and absolute countsThe percentage ranges MedlinePlus quotes beside the absolute ranges five laboratories print, why the same result is flagged at one lab and not another, children, Duffy-null and pregnancy, and two worked examples.Published · 21 min read
How to count bacterial colonies and work out CFU per mLWhich countable range belongs to which method, TNTC and too few to count, and CFU per mL worked twice.Published · 13 min read
How to do a manual differential countWhy the pattern matters, how many cells is enough, and the imprecision built into the method itself.Updated · 11 min read
Other topics: counting and tallying, sports scoring and rules, writing and word counts, health, fitness and habits, prayer beads and crafts, or every guide on the guides front page.