Automated cell counters have been around for some time now, both in biological research labs and medical test/research centers. It is indeed a timesaving tool for researchers and professionals of the medical sector alike. But the hands-on approach of the manual counting of cells using a hemocytometer seems to still win the battle. What are the reasons for this?
Automated cell counters rely on different principles depending on the type: some use impedance, which varies when a cell passes through the electrical path, while others feature a light source in the form of a laser, which is directed to the cell suspension flow and detected on the other side of the tubing (until a cell crosses and is therefore counted). Automated cell counters can also use both to provide an enhanced accuracy on the reading.
There are also disadvantages to the manual cell counting with a hemocytometer, mainly in terms of manipulation errors (improper mix) and human sampling errors (over-counting or under-counting of specific cell types or in specific areas). But this can also be an advantage. Why? Researchers taking care of cell cultures need to keep track of what is happening in there. If they actually proceed with the cell count themselves, they get to analyze visually the cell sthey count, and any anomaly can be detected sooner rather than later. It is also important for newer member of the research team to familiarize themselves with the traditional techniques and the cell morphology, as this usually determines the healthiness of a cell culture.
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Why are people still using slow and inaccurate hemocytometers?
The reason why you should use an automated cell counter (if you can afford it) is not only ease and speed but more importantly for increased accuracy and precision. Automated cell counters like the Cellometers often count over 1000 cells per sample in a few seconds, and count in the exactly the same way each time. The biggest flaw of the hemocytometer counting is humans – subjective, incosistent and error prone. Biology has even advanced from Trypan Blue to the more sensitive AOPI vaibaility dye gives a clear green for live and red for dead output.
That’s a great question!
It appears the machines you’re talking about are $3000 or more, and use consumables (which is wasteful) that are ~$1/count. A hemocytometer costs ~$175 total. A measurement on the former might be fast, but you’re only saving yourself a few minutes per measurement, minutes which can be shortened further by using my app, Hemocytometer Sidekick.
You would have to be doing a lot of cell counting (say, a hospital pathology lab), or require the other special functions the machine has, to make that purchase worthwhile.
Automated counters aren’t perfectly accurate, and depends a lot on what you’re looking for. I’m aware of some scientists who went back to hemocytometers after trying an automated one. Even if the machine you mention is perfectly accurate, not all applications need that degree of accuracy. Humans aren’t *that* bad at counting cells.
Fluorescent dyes are fine, but that requires a fluorescence microscope, which is much more expensive than a basic light microscope. And again, for many applications the error from Trypan Blue may be inconsequential.
Hemocytometers are used by brewers, veterinarians, biologists out in the field, and those who only need to count occasionally. Automated is great for high-throughput core labs or those that absolutely require a reproducible, traceable measurement.
How do haemocytometer methods for counting microbes differ to plating techniques?
Great question!
With a hemocytometer, you can get a count of individual cells, both live and dead, at a point in time. With plating, you only count the live and growing cells, and have to wait ~24 hours to get a result. Those growing cells, though, are “colony forming units”, which may be a clump rather than an individual cell. Plating may be better for large scale counting as well, and the count can essentially be preserved for a longer period.