Blood And…

Please refer to first image in the previous post for clarity. -K

Where can blood smears be acquired?

The first two slides were purchased as part of larger collections from a student cleaning house in the first instance, and a collector in the second. If one wishes similar specimens know that they are generally not on the expensive side (as far as prepared slides go) and available wherever second-hand goods of a curious sort may be had. The second two slides and others of similar sort are available singly, or as components of general sets from dealers in educational materials. Without being too indirect let me just comment that Carolina is an excellent source if one elects to purchase commercially prepared slides of considerable quality.

As an obvious alternative, one may produce blood smears of their own without excessive trouble or exotic materials. A few slips, a stain or two and a pin are the bare minimum of supplies required. Unfortunately, things get tricky here. Blood smears are usually produced for a particular diagnostic purpose, and although they may be safely made by an amateur, it’s a medical procedure and can present some hazards. One may hardly rush about pricking friends and family with a pin for the sake a few drops of blood and a bit of curiosity. Blood-borne pathogens are very real and potentially dangerous, so that pin mentioned above is right out.

What is needed to make one?

Toss out that pin and replace it with a sterile lancet. Pharmacies provide an extensive selection of disposable lancets and reusable lancing devices for diabetics. One can purchase a box of one hundred single use sterile lancets for a few dollars and a compatible variable depth lancing pen for a few more. Spring-loaded disposable lancets are an option as well but might not be as readily available.

Any two slips of the traditional one by three inch size may be used. It is often best to select high quality slips of one millimeter thickness however, cleanliness is the most important factor for success with smears; fine smears may be made on the cheapest economy slips, provided they are clean. It’s worth noting that although the smear may be made upon any slip it is most easily produced when using a slip with plain cut edges, beveled or ground edged slips may be used but are apt to result in difficulty.

Cover slips are not absolutely necessary, but if desired one should use the largest possible and ensure all are of a thickness for which ones objectives are corrected. It may occasionally be best to form the smear directly on the cover slip and in that case one should avoid circular covers.

If employing a cover slip one will need a mountant. Any of the standard permanent mounting mediums will do. For most users this will mean Euparal or Balsam. When using balsam it should be as neutral in pH as possible as acidity will tend to bleach the stains more or less rapidly. Histomount, Mount-Quick, SHUR/mount, Meltmount, and any other of the modern permanent mountants may be used with only slight modification to the smear preparation as required.

Stains are a must when it comes to blood smears. Wright’s stain is perhaps the most popular, followed by hematoxylin and eosin (H&E). Depending on the supply of stain one already has on hand it is possible to prepare a suitably stained preparation with any of numerous combinations. Eosin and methylene blue may be used individually to produce an effect identical to that of Wright’s stain (which is of course a combination of eosin and methylene blue in methyl-alcohol). Giemsa, on its own or in conjunction with Wright’s is a popular option as well. It is always possible to try whatever is on hand provided one is familiar with its action.

What else is needed?

Nothing, nothing else is absolutely needed. At it’s most basic one needs only two slips, a drop of blood, a bit of stain, and access to running water. The next step beyond requires only the addition of a cover slip and mountant. Different sources might lead one to believe that a host of other supplies are required. Access to a Bunsen burner or hot plate is frequently required in historic methods, notably the Ehrlich method. A dozen Coplin jars and different solutions for each might be called for in others. One might be directed to add normal saline or buffer solutions to the smear while staining. Some works see fit to recommend methyl-alcohol as a fixative or drying bath.

All the extras are really just that, extra. While specialized methods are recommended for particular needs, all the extras are truly superfluous for smears intended only for general examination. If one happens to have other materials on hand and wishes to employ them effectively the points at which they come into play will be mentioned when the process is explained in the next posting. It is no great loss if only the basics are employed.

The bare minimum for a blood smear.

The bare minimum for a blood smear.

Next time: making the smear!


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