The Principles of Clinical Cytogenetics - Extra Materials - Springer

Quality Control and Quality Assurance 103
Computerized Imaging Systems
Computer-driven imaging systems are essentially the digital equivalent of photography; otherwise,
the steps involved are similar. Instead of photographing a cell, it is electronically captured in
digital form. Instead of developing film and using filters to produce prints with the appropriate contrast
and background, the image is electronically enhanced to achieve a similar appearance, and a
laser or other type of printer provides a hard copy. Finally, images are stored not as photographic
negatives but as digital files on tape drives, optical disks, DVD-R, or other digital storage media.
Finally, as with photography, an understanding of theory and hardware, generated by the appropriate
amount of training, are required so that laboratory staff can utilize an imaging system properly
and efficiently. (See Chapter 7.)
Karyotype Production
Although not used in all countries, the final laboratory manipulation required for chromosome analysis
is typically the generation of the ordered arrangement of chromosomes known as a karyotype.
If there was ever a perfect example of the value of training in laboratory medicine, it is this process.
A bright individual with a modest comprehension of the theory behind cytogenetics and essentially
normal pattern-recognition and motor skills can be taught the normal human karyotype well
enough to perform this task in about a week. Yet, the comment most often made by visitors to a
cytogenetics lab is typically, “These chromosomes all look alike. How do you tell them apart? I’d
never be able to do that.” In reality, all that is required is a sufficient number of images for repeated
attempts, plus sufficient patience on the part of the individuals doing the training. By making attempt
after attempt (and receiving the appropriate corrections each time), one eventually begins to recognize
certain pairs, and then eventually all pairs. Mastery of the subtleties, sufficient to perform actual
microscopic analysis, of course requires much more training, but in many laboratories, lab aides,
interns, or other students are often employed to generate karyotypes. A good rule to follow when this
occurs is that no such individual is permitted to karyotype an entire case without supervision or
review by a trained technologist.
Karyotype production is one method laboratories use to divide analyses between two or more
technologists. This can be accomplished with a guideline that specifies that the technologist(s) who
performed the microscopic analysis cannot prepare or review the karyotypes for that patient. When
one adds to this a review by the laboratory supervisor or another senior individual, followed by final
review by the laboratory director, it can be seen that a well-designed protocol can ensure that at least
four or more trained “pairs of eyes” examine chromosomes from every patient, increasing the likelihood
of detecting a subtle abnormality or clerical error.
A special consideration in this area involves the use of the computerized imaging system to prepare
patient karyotypes. In the past this essentially involved “cutting and pasting” the chromosomes
with a trackball or mouse; however, pattern-recognition software has improved to the point that many
sophisticated systems can now arrange the chromosomes with little or no human input (see Chapter 7).
This, of course, creates a quality concern. Laboratories deal with this by putting in place protocols
that require appropriate review of all computer-generated karyotypes. When properly monitored,
such systems can increase laboratory efficiency by markedly reducing the time required for karyotype
production.
POSTANALYTICAL TESTING COMPONENTS
Preliminary and Final Reports
Reporting the results of chromosome analysis can have a direct impact on the diagnosis and treatment
of a patient. Considering this, it is important to establish a reporting procedure that accomplish
the following: