The finding of a prolonged bleeding time in a patient whose platelet count is normal suggests some abnormality in the function of the platelets. This situation may be due to an inherent platele

Khali D Hassan

Normal School Children

Roshidah Ishak

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Med. J. Malaysia Vol. 42 No. 1 March 1987
SCREENING FOR
PLATELET ABNORMALITIES IN
NORMAL SCHOOL CHILDREN
IN KUALA LUMPUR
ROSHIDAH ISHAK
KHALI D HASSAN
INTRODUCTION
The finding of a prolonged bleeding time in
a patient whose platelet count is normal suggests
some abnormality in the function of the platelets.
This situation may be due to an inherent platelet
defect or to the deficiency of a plasma factor
necessary for some aspect of platelet function.
Defects of platelet function are also seen in a
wide range of disease states and may be caused by
many different classes of drugs.!
Simple methods are available to identify
abnormalities in platelet numbers and/or function.
Tests of platelet aggregation, using the aggrego-
meter, are now widely used to investigate patients
suspected of having platelet disorders.
We observed in the last four years that throm-
bocythopenia is quite common amongst children
and bleeding fram platelet dysfunction, congenital
or acquired, is not rare in Malaysia.
This study was done to assess the prevalence of
platelet abnormality in a section of the general
'healthy' population of school-going children and
to study the possible causes of any abnormalities
detected.
MATERIALS AND METHODS
A total of 1,299 school children, age ranging
from ten to twelve years, from various schools in
Roshidah Ishak, BSc (Hons)
Khalid Hassan, MBBS, MRCP, MRCPath,
DCP, DTM & H
Division of Haematology
Institute for Medical Research
Jalan Pahariq, 50588 Kuala l.urnpur. Malaysia
36
the Federal Territory was screened for platelet
dysfunction. Consent from the parents or
guardians was obtained prior to the investigation.
In addition to the routine medical and family
history and physical examination, measurements
of the bleeding time, platelet counts and whole
blood clot retraction were made at the time of
study; stools were collected for detection of
ova and cysts. Any child on any drug within the
last two weeks prior to the screening was rejected.
The test of bleeding time was done by a single
person throughout, using Duke's method" and
the observation for whole blood clot retraction
was made after one hour incubation following
the formation of a clot." Platelet counts were
obtained using the Ultra-Flo 100 by Clay Adarns"
and the detection of ova and cysts by the direct
method. All subjects had their stained peripheral
blood films examined for any evidence of haema-
tological abnormalities.
Abnormalities in any of the measurements
taken would be followed up with a platelet func-
tion test using the Chrono- Log aggregometer
(Chrono-Log Corp.. Pennsylvania), by the method
of Born."
RESULTS
Table I shows the number of school children
screened by ethnicity. Only four cases were
found to have a bleeding time of more than ten
minutes at the time of initial investigation. The
normal value for the bleeding time in this study
was taken to be less than ten minutes. The distri-
bution curve (histogram) for these values is shown
in Fig. 1. The bleeding time obtained in this studyTABLE I
NUMBER OF SCHOOL CHILDREN SCREENED BY
ETHNICITY
Ethnic group No. screened % from total
Malays 526 40.7
Chinese 573 44.1
Indians 200 15.4
ranges from one to sixteen minutes with a mean of
three minutes.
The platelet count, whole blood clot retraction
and stool investigations were found to be normal
in all the cases mentioned above. A repeat of all
the measurements in all the four cases, done a
few months later, were found to be normal. Due
to this finding, no further follow-up tests were
done.
Two cases of low platelet counts, 105 x 10
9 /1
and 100 x 10
9 /1 respectively, were found amongst
the screened school children but their bleeding
times were within normal limits. Both these cases
were boys. No abnormalities were detected in the
other measurements done for these two cases,
and a repeat examination, done several months
later, revealed normal values. The distribution
curve (histogram) for the platelet counts in the
children studied is shown in Fig. 2.
DISCUSSION
The bleeding time has been used as a screening
test for platelet dysfunction in our laboratory for
many years. The Duke's method was utilised
due to its inexpensive apparatus and the simple
technique required to carry out the test. This
method, though reproducible, has been shown to
be less sensitive than the Ivy's method using the
template in detecting moderate bleeding dls-
orders.f It also has a wider normal range as
compared to the Ivy's method. In our experience,
a Duke bleeding time greater than ten minutes
always represents a clinically significant abnormal
bleeding time.
Though the bleeding time in the four cases
was found to be more than ten minutes at the time
of initial investigation, a repeat of the bleeding
time a few months later gave normal values. This
might suggest an acquired platelet dysfunction
which has corrected itself. The fact that many
16
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ri ····rnn .......
0.5 1.6 2.7 3.9 5.0 6.1 7.2 8.3
Bleeding time in minutes
Fig. 1 The distribution curve (histogram) for the bleeding time values. (Note: the computer printout includes a normal
Gaussian curve, shown in dotted line,for comparison.)
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150 222 293
Platelet count (x
365 436
microlltra)
508 580 651
Fig. 2 The distribution curve (histogram) for the platelet counts" (Note: the computer
curve, shown in dotted lines, for comparison.]
includes a normal Gaussian
classes of drugs and some food could cause defects
in the platelet function which give rise to
prolonged bleeding time has not been overlooked,
but it would be difficult to prove this relationship
in any of the cases. The four cases (two Chinese
and two Indians) denied taking any drugs or tradi-
tional herbs. The possibility that the prolonged
bleeding time in the cases mentioned above was
caused by drugs ingested prior to the investiga-
tion, even in the absence of a positive drug history,
cannot be ruled out, as the ch ildren might not be
aware of what was given to them by their parents
in the two weeks prior to the tests. Many tradi-
tional remedies given for minor ailments may
contain compounds that can compromise platelet
function.
Thrombocytopenia is not uncommon amongst
children with bleeding disorders referred to this
Division. Over the past four years (1982 - 1985
inclusive), of 55 children with bleeding disorders
seen in this Division, nine were due to some defect
in platelet functions and five due to low platelet
count. In this study, however, only two cases of
low platelet counts were obtained. Neither of
them had a prolonged bleeding time; there were
sufficient numbers of platelets present (counts
38
of 100 X 10
9 /1 and 105 x 10
9 /1 respectively)
to ensure adequacy in function in vivo. The
counts returned to normal several months later.
Viral infections are said to cause a thrombocyto-
penic condition. Since there was no evidence of
viral infection in the peripheral blood film, no
serological tests were done, but subcl inical viral
infection cannot be ruled out. Drugs and chemicals
have been shown to be a common cause of
moderate to severe thrombocytopenia. However,
in neither case was a history of exposure to drugs
or chemicals elicited.
From the" results obtained in th is study, we
conclude that the prevalence of the platelet
dysfunction in the general 'healthy' population
of school-going children in this country is very
low. The investigation into the possible causes of
abnormalities in the platelet function was not
accomplished due to the absence of any case of
persistent platelet dysfunction amongst the school
children screened. The chances are that such dys-
functions probably reflect subclinical viral
infections which explain its transient nature.
Thrombocytopenia is also a rare finding and,
again, transient in nature; the probability is,
again, that viral infections are responsible forcausing these transient mild depressions in the
platelet count without any outward clinical
effect, although this is difficult to prove.
ACKNOWLEDGEMENTS
We are grateful to the staff of Coagulation
Laboratory, Haematology Division, Institute for
Medical Research, Kuala Lumpur, Malaysia for
their technical assistance.
REFERENCES
1 Weiss H J. Platelet physiology and abnormalities of
platelet function (second of two parts), The New Eng-
land Journal ofMedicine 1975; 239(12): 580-587.
39
2 Duke W W. The pathogenesis of Purpura bem orr-
hagica with a special reference to the part played by
blood platelets. Arch Intern Med 1912; 10 : 445.
3 Macfarlane R G. The coagulation action for measuring
clot retraction. Lancet 1961; i : 1199.
4 Adam W, Schulz J, Kratt E. The electronic counting of
thrombocytes from whole blood. Blut 1976;32 : 347-
352.
Born G V R. Aggregation of blood platelet by adeno-
sine diphosphate and its reversal. Nature 1962; 194
927.
6 Ivy A C, Nelson D, Bucher G. The standardisation of
certain factors in the cutaneous 'venostasis' bleeding
time technique. J Lab Clin Med 1940; 26 : 1812.

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