The T-prep technique is a simple pull preparation method, which produces one readable long slide for each drop of marrow used. It does not require much manual dexterity or practice to obtain usable smears. Since this method only produces one usable smear per drop and requires a moderate size drop of marrow, it is not a preferred technique for small samples. However, it is easy to learn and is frequently used by clinicians.
To perform this procedure, a drop of bone marrow is placed in the center of a slide (cross bar) and a second slide (post) is placed over it; oriented so the combination looks like the letter t. The marrow is allowed to spread between the two slides while the slide that is on the top (post slide) is pulled across the bottom slide (cross bar). This produces one slide with the bone marrow smear on the top slide. The bone marrow smear should cover approximately 3-4 inches in length.
This technique can be performed sequentially with a series of 5-6 slides in a row with a drop of marrow quickly placed on each slide. The bone marrow drops can originate directly from the aspirate syringe at the patient bedside or from a transfer pipitte, collecting sample from an anticoagulated bone marrow tube. Once the first smear is made, the slide that initially had the drop of marrow becomes the top (post) slide for the next prep. By reusing the bottom slide, which no longer has any sample on it, one can minimize the amount of workspace required at bedside as well as reduce material wastage.
Because the bone marrow is allowed to spread between two slide surfaces before the prep is pulled/smeared, any spicules present will be spread in a monolayer permitting good cellular identification. However, since only a limited number of smears are usually made, it is less useful for certain leukemia patients where many slides are required for special stains in addition to the normal morphology smears.