Clinical implications of elevated antiphospholipid antibodies in adult patients with primary immune thrombocytopenia.

Abstract

Antiphospholipid antibodies (aPL) have been detected in various proportions of patients with primary immune thrombocytopenia (ITP), but the clinical significance of this is debatable. The present study aimed to determine the frequency and clinical implications of elevated aPL in adult patients with ITP.
We prospectively studied newly diagnosed adult patients with ITP who were enrolled between January 2003 and December 2008 at Chungnam National University Hospital. They were evaluated for the presence of lupus anticoagulant (LA) and anticardiolipin antibodies (aCL) at diagnosis and were followed for the development of thrombosis.
Seventy consecutive patients with ITP (median age, 48 years; range, 18 to 79) were enrolled. Twenty patients (28.5%) were positive for aPL at the time of diagnosis: aCL alone in 15 (75%), aCL and LA in two (10%), and LA alone in three (15%). Patients who had platelet counts < 50,000/µL were administered oral prednisolone with or without intravenous immune globulin. No difference was found between the aPL-positive and -negative groups regarding gender, initial platelet count, and response to the therapy. After a median follow-up of 20 months (range, 2 to 68), two of 20 patients who were aPL-positive (10%) developed thrombosis, whereas no thrombotic event was found among those who were aPL-negative.
Our data suggest that aPL levels should be determined at the initial presentation of ITP and that patients found to be aPL-positive should receive closer follow-up for thrombotic events.

Full text

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ORIGINAL ARTICLE
korean j intern med 2011;26:449-454
http://dx.doi.org/10.3904/kjim.2011.26.4.449
pISSN 1226-3303 eISSN 2005-6648
http://www.kjim.or.kr
Clinical Implications of Elevated Antiphospholipid Antibodies
in Adult Patients with Primary Immune Thrombocytopenia
Young-Joon Yang1, Gak-Won Yun2, Ik-Chan Song2, Seung-Woo Baek2, Kyu-Seop Lee2, Hye Won Ryu2,
Myung-Won Lee2, Hyo-Jin Lee2, Hwan-Jung Yun2, Samyong Kim2, and Deog-Yeon Jo2
1Department of Internal Medicine, Daejeon Saint Mary’s Hospital, The Catholic University of Korea School of Medicine;
2Department of Internal Medicine, Chungnam National University School of Medicine, Daejeon, Korea
Background/Aims: Antiphospholipid antibodies (aPL) have been detected in various proportions of patients with primary
immune thrombocytopenia (ITP), but the clinical significance of this is debatable. The present study aimed to determine
the frequency and clinical implications of elevated aPL in adult patients with ITP.
Methods: We prospectively studied newly diagnosed adult patients with ITP who were enrolled between January 2003
and December 2008 at Chungnam National University Hospital. They were evaluated for the presence of lupus anticoagu-
lant (LA) and anticardiolipin antibodies (aCL) at diagnosis and were followed for the development of thrombosis.
Results: Seventy consecutive patients with ITP (median age, 48 years; range, 18 to 79) were enrolled. Twenty patients
(28.5%) were positive for aPL at the time of diagnosis: aCL alone in 15 (75%), aCL and LA in two (10%), and LA alone in
three (15%). Patients who had platelet counts < 50,000/µL were administered oral prednisolone with or without intravenous
immune globulin. No difference was found between the aPL-positive and -negative groups regarding gender, initial platelet
count, and response to the therapy. After a median follow-up of 20 months (range, 2 to 68), two of 20 patients who were
aPL-positive (10%) developed thrombosis, whereas no thrombotic event was found among those who were aPL-negative.
Conclusions: Our data suggest that aPL levels should be determined at the initial presentation of ITP and that patients
found to be aPL-positive should receive closer follow-up for thrombotic events.
Keywords: Antibodies, anticardiolipin; Antiphospholipid syndrome; Purpura, thrombocytopenic, idiopathic; Lupus coagula-
tion inhibitor; Thrombosis
INTRODUCTION
Primary immune thrombocytopenia (ITP) is an ac-
quired disorder characterized by isolated thrombocyto-
penia resulting from autoantibody-mediated peripheral
platelet destruction and the absence of any obvious initiat-
ing and/or underlying cause of the thrombocytopenia [1].
Antiphospholipid syndrome (APS) is a thrombotic dis-
order defined by the presence of one or more clinical fea-
tures of arterial or venous thrombosis, recurrent fetal loss,
and presence of antiphospholipid antibodies (aPL) such as
anticardiolipin antibody (aCL), lupus anticoagulant (LA),
and/or anti-b2 glycoprotein-I (anti-b2GPI) [2-4]. Throm-
bocytopenia, as a manifestation of primary APS, has a
reported prevalence of 20 to 46% [5-7]. Although evidence
suggests that aPL may bind activated platelet membranes
Copyright © 2011 The Korean Association of Internal Medicine
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-
commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Received : June 6, 2011
Revised : July 26, 2011
Accepted : October 11, 2011
Correspondence to Deog-Yeon Jo, M.D.
Division of Hematology/Oncology, Department of Internal Medicine, Chungnam National University Hospital, 33 Daesa-dong, Jung-gu, Daejeon 301-721,
Korea
Tel: 82-42-280-7162, Fax: 82-42-257-5753, E-mail: deogyeon@cnu.ac.kr

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450 The Korean Journal of Internal Medicine Vol. 26, No. 4, december 2011
http://dx.doi.org/10.3904/kjim.2011.26.4.449
http://www.kjim.or.kr
and cause platelet destruction [8,9], the pathogenesis of
thrombocytopenia related to aPL remains unclear. Con-
versely, elevated levels of aPL have been demonstrated in
patients with ITP. The reported incidences of aPL in ITP
vary considerably, ranging from 26 to 75% of cases, which
can be attributed partly to technical differences [5-8,10-
13]. Furthermore, the clinical significance of aPL in pa-
tients who have ITP is controversial. Recently, an interna-
tional working group reported that measuring aPL is not
routinely recommended for investigation of ITP [1]. How-
ever, the prevalence of aPL and its clinical implications in
ITP have not been studied in Korean populations. Here,
we performed a prospective study to define the frequency
and clinical relevance of aPL in a single-center cohort of
adults with ITP.
METHODS
Patients
We prospectively enrolled patients who were newly di-
agnosed with ITP between January 2003 and December
2008 at Chungnam National University Hospital. ITP
was diagnosed based on the guidelines proposed by the
American Society of Hematology [14]. Only patients aged
> 18 years who had platelet counts < 100,000/µL and no
history of other clinical conditions that can cause throm-
bocytopenia were included. All patients underwent a panel
of laboratory tests, including tests for antinuclear and anti-
virus (cytomegalovirus, Epstein-Barr virus) antibodies,
and screening for human immunodeficiency virus (HIV),
and hepatitis B and C virus infection. Peripheral blood
and bone marrow smears were examined to exclude other
causes of thrombocytopenia. Patients who had a history of
arterial or venous thrombosis were excluded. Additional
exclusion criteria were a history or clinical findings of APS
fulfilling the international consensus statement criteria
[3], systemic lupus erythematosus (SLE) satisfying the
American College of Rheumatology criteria [15,16], other
autoimmune disorders, malignancies, and concomitant
viral infections, including HIV or hepatitis C or B virus in-
fection.
Laboratory investigation
Detection of LA
Blood samples were collected in vacuum tubes contain-
ing sodium citrate. Dilute Russell’s viper venom time
(dRVVT) was used as an initial sensitive screening test
for LA and as a confirmatory test. Criteria for positive LA
were based on the guidelines of the Scientific Subcommit-
tee of the International Society on Thrombosis and Hae-
mostasis [17]. Patients in whom a ratio > 1.2 (test dRVVT/
control dRVVT) was obtained were considered to be posi-
tive.
Detection of aCL
Blood samples were collected in serum tubes. IgM-
aCL and IgG-aCL tests were performed using an enzyme-
linked immunosorbent assay (ELISA) for semiquantitative
detection in human sera. The values of aCL are expressed
in MPL and GPL (units of IgM-aCL and IgG-aCL, respec-
tively). Twenty GPL units/mL for IgG and 20 MPL units/
mL for IgM were considered to be positive results.
Treatment of ITP
Patients with platelet counts < 50,000/mL were placed
on prednisolone (PD) therapy. PD was administered at a
dose of 1 mg/kg/day for 4-6 weeks, and then was tapered.
In patients with initial platelet counts < 20,000/mL, in-
travenous immune globulin (IVIg) was administered at a
dose of 400 mg/kg/day for 5 days in combination with PD.
Splenectomy was performed in patients who were refrac-
tory to PD. Response was defined as 1) a platelet count ≥
100,000/µL at the last clinic visit, when the initial platelet
count was > 50,000/µL; or 2) a platelet count increase of
≥ 20,000/µL from baseline to a final value > 50,000/µL.
Responses lasting < 3 and ≥ 3 months after the initiation
of treatment were defined as transient and sustained re-
sponses, respectively.
Follow-up
Eligible patients were monitored every 1-2 weeks for the
first 3 months and then every 1-3 months for the remain-
ing period, to conduct laboratory investigations and check
for the development of arterial or venous thrombotic
events. A complete blood count was determined at every
visit. Routine chemistry, urine analysis, studies to exclude
SLE, and aPL tests were performed 12 months apart.

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Statistical analysis
Characteristics, response to treatment, and frequency
of thrombosis were compared between aPL-positive and
-negative patients using the chi-square test as appropriate
for categorical variables and Student’s t test for continuous
variables. A p value < 0.05 was considered to indicate sig-
nificance. All analyses were performed using SPSS version
17.0 (SPSS Inc., Chicago, IL, USA).
RESULTS
Patient characteristics and frequency of aPL at the
time of ITP diagnosis
Seventy patients were enrolled. The median age was
48 years (range, 18 to 79), and 45 patients (64.3%) were
female. Most of the patients (91.4%) had platelet counts <
50,000/mL (Table 1). Of these, aPL (aCL and LA) were de-
tected in 20 patients (28.5%): aCL alone in 15 (75%), aCL
and LA in two (10%), and LA alone in three (15%). Of the
15 patients who were positive for aCL only, eight had IgG-
aCL only, four had IgM-aCL only, and three had both IgM-
and IgG-aCL. LA was detected in a total of five patients
and was associated with aCL in two (Table 2). Age, gender,
and platelet count did not differ between the aPL-positive
and -negative groups (Table 1).
Response to treatment
Sixty-four of the 70 patients (17 aPL-positive; 47 aPL-
negative) received PD therapy with or without IVIg. Six of
the 70 (those with initial platelet counts > 50,000/µL) did
not receive any therapy. All patients who received therapy
exhibited a transient or sustained response. Both tran-
sient and sustained response rates were similar between
the aPL-positive and -negative groups (Table 3). The time
to response did not differ between the aPL-positive and
Table 1. Patient characteristics at the time of ITP diagnosis
CharacteristicsAll aPL-positive aPL-negativep valuea
No. of patients702050
Age, median (range), yr 48 (16-79) 45 (20-76) 49 (16-79)0.432
Gender
Male25 916
0.305
Female 4511 34
Platelet count, /mL
Mean ± SD 14,360 ± 17,000 16,250 ± 16,80013,600 ± 18,0000.573
< 50,000, n (%)64 (91.4)18 (90) 46 (92)
0.830
≥ 50,000, n (%)6 (8.6) 2 (10)4 (8)
ITP, immune thrombocytopenia; aPL, antiphospholipid antibody.
ap value between the aPL-positive and -negative groups.
Table 2. Distribution of elevated aPL at ITP diagnosis
aPL status
All patients
(n = 70)
8 (11.4)
Platelet count, /μL
< 50,000 (n = 64)
7 (10.9)
≥ 50,000 (n = 6)
1 (16.7)IgG-aCL
IgM-aCL 4 (5.7) 3 (4.7)1 (16.7)
IgG-aCL + IgM-aCL3 (4.3)3 (4.7)0 (0)
LA + IgG-aCL1 (1.4)1 (1.6)0 (0)
LA + IgM-aCL1 (1.4) 1 (1.6) 0 (0)
LA + IgG-aCL + IgM-aCL0 (0) 0 (0) 0 (0)
LA3 (4.3) 3 (4.7) 0 (0)
Total 20 (28.5)18 (28.1) 2 (33.3)
Values are presented as number (%).
aPL, antiphospholipid antibody; ITP, immune thrombocytopenia; aCL, anticardiolipin antibody; LA, lupus anticoagulant.

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-negative groups, regardless of treatment modality (Table
3).
Status of aPL during follow-up
Most patients (88.5%; 62 of 70) were followed with aPL
tests 12 months apart, 85.0% (17 of 20) in the aPL-positive
group and 90.0% (45 of 50) in the aPL-negative group. No
patient who was aPL-positive at the time of ITP diagno-
sis lost aPL positivity, and none of those who were aPL-
negative at the time of ITP diagnosis displayed aPL during
follow-up (data not shown).
Thrombotic events during follow-up
The median follow-up periods in the aPL-positive and
-negative groups were 19.6 (interquartile range, 15.5 to
27.5) and 20.7 (18.7 to 28.1) months, respectively. The 50
patients who did not have aPL at diagnosis did not dis-
play thrombotic events during a median follow-up of 20
months (range, 2 to 68). In contrast, two of the 20 aPL-
positive patients (11%) experienced thrombotic events
(Table 3).
A 54-year-old man who had atrial fibrillation developed
acute myocardial infarction 2 months after diagnosis of
ITP. Platelet counts at diagnosis and the thrombotic event
were 39,000/mL and 61,000/mL, respectively. He had IgM-
aCL, but not LA or IgG-aCL, at diagnosis of ITP. He had
discontinued PD 2 weeks before the thrombotic episode.
He underwent successful intracoronary stenting and re-
ceived aspirin as prophylaxis. Another patient, a 56-year-
old woman, had LA, a high level of IgM-aCL (29.7 MPL
Table 4. Characteristics of the two patients who developed thrombosis
At diagnosis follow-up (12 mon apart)
No.Age Gender
At development of thrombosis
Months after
diagnosis
AMI
2
Cardiovascular risk
factors
PLT, /mL LA IgG-aCLIgM-aCL Type
PLT, /mL
1 54 Male 39,000--+ 61,000 Atrial fibrillation
78,000--+
2 56 Female
31,000+-+
DVT
5 12,000 Obesity
105,000+-+
PLT, platelet count; LA, lupus anticoagulant; aCL, anticardiolipin antibody; AMI, acute myocardial infarction; DVT, deep vein thrombosis.
Table 3. Response to treatment and clinical course according to aPL status
Outcomes
Total
(n = 70)
6 (8.6)
aPL-positive
(n = 20)
3 (15.0)
aPL-negative
(n = 50)
3 (6.0)
p valuea
TreatmentNo
0.188
yes64 (91.4) 17 (85.0) 47 (94.0)
Response
IVIg + PD Transient response26/55 (47.3) 8/15 (53.3)18/40 (45.0)
0.581
Sustained response29/55 (52.7) 7/15 (46.7) 22/40 (55.0)
Pd Transient response4/9 (44.4) 1/2 (50.0) 3/7 (42.9)
0.236
Sustained response 5/9 (55.6)1/2 (50.0) 4/7 (57.1)
OverallTransient response30/64 (46.9) 9/17 (52.9) 21/47 (44.7)
0.409
Sustained response34/64 (53.1) 8/17 (47.1)26/47 (55.3)
Time to response, day
IVIg + PD- 2.3 (1-12) 2.9 (1-15) 0.716
Pd- 7.3 (2-26) 5.9 (1-34)0.496
Splenectomy 4 (5.4) 1 (5.0) 3 (6.0)0.871
Thrombotic event 2 (2.9) 2 (10.0) 0 (0) 0.023
Values are presented as number (%) or median (range).
aPL, antiphospholipid antibodies; IVIg, intravenous immune globulin; PD, prednisolone.
ap value between the aPL-positive and -negative groups.

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units/mL), and obesity. She developed deep vein thrombo-
sis (DVT) 5 months after the diagnosis of ITP. Her platelet
counts at diagnosis and the thrombotic event were 31,000/
mL and 12,000/mL, respectively. She was taking PD at the
time of development of DVT. No patient received IVIg, da-
nazol, or underwent splenectomy during the 2 weeks pre-
ceding the thrombotic events (Table 4). Although the two
patients had risk factors other than aPL for thrombosis,
thrombotic risk factors did not differ as a function of aPL
status (Table 5).
Pregnancy during follow-up
Among the 27 women of child-bearing age, seven (25%)
were aPL-positive, and three had become pregnant after a
median follow-up of 37 months (range, 10 to 86). No mis-
carriage occurred in either the aPL-negative or -positive
groups (data not shown).
DISCUSSION
A variable number of patients with ITP have aPL at the
time of diagnosis and during follow-up after treatment. In
the present study, more than one-fourth of patients with
ITP (28.5%) had aPL at the time of diagnosis. This was
similar to or lower than previously reported rates [5-8,10-
13]. The reason underlying this discrepancy is not clear.
Additionally, controversy still exists regarding the clinical
significance of aPL in these patients. Nevertheless, bleed-
ing manifestations, platelet counts, and response to cor-
ticosteroid treatment have been repeatedly demonstrated
to not differ as a function of aPL status at the time of di-
agnosis. The present study confirmed that the presence or
absence of aPL was not associated with a specific clinical
presentation and did not affect treatment responses in pa-
tients with ITP.
Thrombocytopenia has been reported to have a preva-
lence of 20 to 46% in patients with primary APS [5-7].
Since the first definitive clinical and pathological descrip-
tion of APS [18], the association between aPL and the de-
velopment of thrombosis has been extensively investigated
over decades in patients with APS. However, previous
studies of aPL in ITP have been limited, compared with
those in APS, and only a few clinical studies have exam-
ined the relationship between aPL positivity and risk for
thrombosis. A prospective study on 149 patients with ITP
could identify no relationship between thrombosis and
aPL positivity [8]. In contrast, a similarly designed study
involving 82 consecutive patients with ITP reported that
aPL-positive patients had a greater incidence of thrombo-
sis over a 5-year period (61 vs. 2.3%) [6]. In another study
on 216 patients with ITP, 14 of 55 (25%) aPL-positive pa-
tients developed thrombosis over a 2.5-year period [13]. In
that study, investigators emphasized that thrombosis was
associated with LA, a high IgG-aCL level, and younger age
(i.e., < 45 years) at the time of thrombosis. We found that
two of 20 patients (10%) who were initially positive for aPL
experienced thrombosis during follow-up. One patient
had venous thromboembolism, and the other had arterial
thrombosis. No correlation was found between thrombotic
events and types of aPL, platelet count, steroid therapy,
or age. Patients who were initially negative for aPL never
Table 5. Risk factors for thrombosis according to aPL status
Risk factors
aPL-positive
(n = 20)
3 (15)
aPL-negative
(n = 50)
5 (10)
p valuea
Hypertension 0.553
diabetes mellitus1 (6) 3 (6)0.871
Hypercholesterolemia 1 (6) 4 (8)0.660
Smoking 2 (10) 7 (14)0.652
Infection1 (6)3 (6) 0.871
Surgery0 (0) 2 (4)0.364
Malignancy0 (0) 1 (2)0.524
Obesity 3 (15)4 (8) 0.378
Values are presented as number (%).
aPL, antiphospholipid antibodies.
ap value between the aPL-positive and -negative groups.