Sadly, Mrs Roy wasn't the only
thing nagging at Jonas Roy, 42. A bothersome backache
and persistent night sweats sent Jonas to his GP, who
noted that he had lost more weight since his last visit
and that his glands were still swollen. It was time to
start checking for lymphoma. A lymphoma diagnosis is notoriously
difficult to make. Its variable symptoms allow it to masquerade
as several other conditions. Flow cytometry is commonly
used in diagnosing non-Hodgkin lymphoma (NHL) but this
test hasn't yet been validated. It's a powerful tool that's
capable of detecting minute clonal B-lymphocytes ? a trait
that's believed to be unique to NHL patients. But do people
without lymphoma also share this characteristic?
Researchers at the University of
Texas Southwestern Medical Center in Dallas put flow
cytometry to the test. Dr Steven Kroft and his colleagues
were curious to see whether populations of clonal B-lymphocytes
observed in samples of NHL sufferers could indeed be
used as a diagnostic tool. Their study was published
in the October issue of the American Journal of Clinical
Pathology. The authors said that, "To date, a systematic
assessment of the immunophenotypic spectrum and the
clinical significance of incidentally detected clonal
B-cell populations is largely lacking." It was thought
that the test would yield positive results since the
presence of multiple copies of any one type of B-cell
presumably points to a problem in the body's ability
to shut off B-cell production, a fatal error that can
lead to lymphoma.
The researchers screened 11,500
blood and bone marrow samples, using flow cytometry
to count and type the B-cells in order to find samples
containing clonal populations of B-cells. Of the 93
samples that fit the bill, 69 also had followup clinical
data to indicate whether the patient had developed lymphoma.
In fact, 20 of the 69 patients with clonal B-cell populations
had been subsequently diagnosed with NHL within 40 months
of the sample being taken. However, the other 49 patients
whose blood contained clonal B-cell populations showed
no overt signs of lymphoma. The NHL group did have a
lower mean white blood cell count compared to the lymphoma-free
patients. Otherwise, all 69 patients had similar clinical
and hematologic profiles.
A diagnostic test should distinguish
cells that are going to develop into active lymphoma
from those loitering harmlessly around the lymphatic
system. In this case, however, no differences were found
in the number or type of B-cells between the NHL suffers
and the rest. Therefore, the authors concluded that
this test is not sufficiently predictive of the emergence
of NHL to be a reliable diagnostic tool. Nonetheless,
they did caution that the 49 patients who had not yet
developed lymphoma might want to continue seeing their
doctor on a regular basis.
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