Though labs have largely automated the process of performing CBCs, thanks
to better hematology instruments, hematopathologists agree it’s still
necessary to perform manual peripheral blood smear reviews on a certain
percentage of specimens. But pinpointing the appropriate frequency of
manual blood smear reviews can be tricky. There’s no set formula—too
many manual reviews waste technologists’ valuable time, but too few manual
reviews could threaten the quality of patient care.
Since the number of manual peripheral blood smear reviews a laboratory
performs is so tightly bound to patient population (a sicker patient population
requires more manual reviews), labs can’t tap any real guideline to settle
on an appropriate frequency for the procedure. Until recently, they also
didn’t have any real data to help them compare their manual peripheral
blood smear review rates with those of their peers.
But first-of-its-kind benchmark data are now available in a new CAP Q-PROBES
report, "Rate of Peripheral Blood Smear Review," which explores the current
standard of practice in U.S. labs. "I visit a lot of laboratories, and
I’ve seen some labs that are manually reviewing 60 to 70 percent of their
CBCs, while others are manually reviewing only five to 10 percent of their
CBCs," says David Wilkinson, MD, PhD, professor and chairman of the Department
of Pathology at Virginia Commonwealth University (VCU), Richmond, and
lead author of the Q-PROBES study. The aim of the study, he says, was
to establish a normative distribution of the review rate among participating
laboratories, "and then try to associate certain types of practice with
higher or lower rates of review."
To establish this normative distribution, Dr. Wilkinson and his coauthors—David
Novis, MD, Jonathan Ben-Ezra, MD, and Mary St. Louis, MT (ASCP)—asked
the 263 participating laboratories to select 10 automated CBCs from each
traditional laboratory shift and determine if a manual review was performed
on the blood smear. For each manual review, patient age, hemoglobin value,
WBC count, platelet count, and primary reason for the review were recorded.
Participants were also asked to determine if the manual review turned
up any new information. The laboratories continued to do this until 60
manual reviews had been collected. The authors then determined manual
review rates, examined demographic and practice parameters, and searched
for associations between review rates and institutions’ demographic and
practice variable information. The study was based on the review of more
than 95,000 automated CBC specimens.
The median laboratory participating in the study manually reviewed 26.7
percent of its automated CBCs, and the mean was even higher, at 28.7 percent.
"I was surprised to learn that more than one-fourth of all CBCs actually
have a technologist look at the smear under the microscope. I would have
expected that number to be lower," says Dr. Ben-Ezra, professor of pathology
and director of hematology laboratories at the Medical College of Virginia
Campus of VCU.
What’s more, 10 percent of the laboratories surveyed were performing
manual reviews of 50 percent or more of their smears. "I would have expected
that number to be less as well," says Dr. Novis, chief of pathology and
medical director of the clinical laboratory at Wentworth-Douglass Hospital,
Dover, NH. From an efficiency standpoint, he says, technology should be
able to reduce that rate.
Neither of these numbers surprised Dr. Wilkinson, who, based on anecdotal
information he collected before the study was launched, suspected that
labs were performing a significant number of manual reviews. Still, he
says, the findings provide useful benchmark data for the clinical laboratory
community. "Not that the median number of manual peripheral blood smear
reviews being performed by labs is anything magic, but if you are a large
lab and you are reviewing 50 to 60 percent of the peripheral smears, and
you can see that half the people in the country are reviewing less than
26 percent of them, then maybe you are doing too many," Dr. Wilkinson
says. "On the other hand, if your review rate is five percent, you may
be doing too few."
Each lab must determine its own cutpoints or triggers for manual review
because patient populations differ, as do clinicians’ needs and desires.
But laboratories can now use the Q-PROBES findings to help them evaluate
and set their own strategies for performing manual peripheral blood smear
reviews, Dr. Wilkinson says.
The study data are broken down in a number of different ways, and the
authors provide insight into what types of labs are performing the fewest
and the most manual reviews, though they note in the analysis that higher
or lower review rates do not necessarily indicate better or worse performance.
As expected, institution size does matter when it comes to manual blood
smear review rates. "The larger the hospital, the greater the percentage
of smears they tended to review," Dr. Ben-Ezra says. "My feeling is that
larger hospitals see more complex clinical cases, and therefore there
are more things that would trigger such a smear review."
Higher rates of manual reviews were often associated with lower efficiency
for the lab in terms of billed tests per full-time equivalent. "The more
labor you put into turning out a CBC result, the more your productivity
drops. That’s self-evident, but now we have documentation of that," Dr.
Novis says. Conversely, lower total review rates and lower leukocyte differential
count review rates were associated with higher productivity ratios.
Also associated with the lower manual review rates and the higher productivity
ratios were automated instrument triggers that were set at a higher threshold
in the labs that performed fewer manual reviews. "Our study showed, for
example, that some labs are now using platelet counts over 1 million as
their cutpoint," Dr. Wilkinson says. "At the 50th percentile, the upper
limit is 800,000, and at the 90th percentile it’s 1 million." A laboratory
whose cutpoint is triggering a manual peripheral blood smear review at
500,000 or 600,000 is in the minority, he adds, because 90 percent of
the labs that participated in the study don’t review a smear unless the
count is higher than that.
Hospitals that have criteria that limit how often they review a smear
manually tend to have a lower rate of review. "However, those criteria
must be hospital-driven," Dr. Ben-Ezra says. "The number of manual reviews
a hospital performs ultimately depends on the needs of the clinical staff,
which in turn depends on the complexity mix of the patients seen at that
How can labs use these data to increase their efficiency? If a lab has
a very high rate of manual differential counts, the less labor-intensive
manual scans may be able to be substituted for the more labor- intensive
manual differential counts, say the study’s authors. Dr. Novis says some
laboratories may be able to use the study’s information on thresholds
to begin a discussion about adjusting the criteria they are using for
what triggers a manual blood smear review.
In addition, he says, if labs want to make changes, they should find
out what their customers want from manual reviews. "I suspect there may
be a disconnect between the users and the providers of this service, given
that our data indicate that only 3.5 percent of the manual diffs or screens
were done at the request of the doctors." Most of them were prompted within
the labs by flags on the instruments. "It may be that if the flags on
the instruments were adjusted a little bit, they could save labs some
time and overhead, without adversely affecting patient care," Dr. Novis
If a lab is determined to find its optimal rate of review, it should
first define what optimal means. "You’d need to go to providers and determine
under what conditions they absolutely need to have a manual smear review
performed, and work backwards from there," Dr. Novis says. "You’d have
to correlate your manual review rates with some kind of clinical outcome.
For example, if certain patients benefited from a review, you would need
to figure out what that benefit might be and then measure it and work
More than 36 percent of the study’s participants reported that when a
manual peripheral smear review was done, useful information was discovered.
This suggests that in many cases the manual reviews uncover something
that the automated instruments might have missed, but there’s no way to
know what that information was, why it might have been useful, and who
found it useful, Dr. Ben-Ezra says. "We don’t have a handle on the type
of information that was gleaned, and consequently we don’t know whether
that median smear review rate of 26 percent is really worth the additional
These are the types of questions laboratories will grapple with as they
use the Q-PROBES data to guide their efforts to boost efficiency, and
it may take another study to generate firm answers. "If this Q-PROBES
is repeated, perhaps the next thing would be to ask both technologists
and physicians if they learned new information from performing the manual
review, and if there is a disconnect there, what it is and why it’s happening,"
Dr. Novis says. "This information alone could allow you to go back and
reset the flags on your instruments and cut down the number of manual
reviews you’re doing."
In an upcoming issue of the Archives of Pathology & Laboratory Medicine,
the study’s authors will discuss the findings in detail, as well as the
activities of some laboratories that are attempting to recommend certain
triggers for manual review. "These triggers are not based on outcome data
or evidence, so more work needs to be done in this area," Dr. Novis says.
In the meantime, labs can use the new Q-PROBES data to make changes. "The
idea is to cut your overhead and increase quality at the same time, and
believe it or not, it is possible," he says.
Sue Parham is a writer in Edgewater, Md. For more information about
the Q-PROBES study (QP043), or for information about other studies, call
800-323-4040 (or 847-832-7000) option 1#.