Ar ¥ vol 10 ¥ nr 5AR • Vol 10 • Nr 5 15.01.2001 16:11 Uhr Seite 231 THE ERYTHROCYTE ADHESIVENESS/AGGREGATION TEST (EAAT) IN THE
PERIPHERAL BLOOD OF PATIENTS WITH ISCHEMIC HEART AND BRAIN
DISEASE WITH NORMAL FIBRINOGEN CONCENTRATIONS
D. Zeltser1, R. Rotstein1, O. Rogowski1, R. Fusman1, I. Shapira1, V. Prochorov1, N. M.
Bornstein2, A. Roth3, G. Keren3, D. Avitzour4, N. Arber5, A. Eldor6, S. Berliner1* Departments of Internal Medicine "D" 1, Neurology 2, Cardiology 3, Gastroenterology 5 and Hematol- ogy6, Tel Aviv Sourasky Medical Center, Tel Aviv, affiliated to the Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel, and Timorim4 Technologies, Jerusalem, Israel * Department of Internal Medicine "D", Tel-Aviv Sourasky Medical Center, 6 Weizman Street Tel Aviv 64239, Israel Phone: x972.3.6973313 Fax: x972.3.6974961 Received: 8.5.2000, Final version: 20.9.2000 ABSTRACT
Previous studies have documented the presence of increased red blood cell aggregability in patients with
ischemic heart and brain diseases. We adapted a simple slide technique and image analysis to reveal the state
of erythrocyte adhesiveness/aggregation (EAA) in the peripheral blood of 206 such patients and in 174 controls.
A significant (P<0.0001) correlation was noted between the EAA state and both fibrinogen concentrations and
erythrocyte sedimentation rate in the whole cohort. Noteworthy was a highly significant increment in the EAA
state in a subgroup of 49 patients who had normal fibrinogen concentrations when compared to matched
healthy controls. This was also the case in 82 patients who had a normal erythrocyte sedimentation rate. Thus,
the EAA assay appears to have the advantage of revealing the presence of acute phase response sticky proteins
not detected by either the erythrocyte sedimentation rate or clottable fibrinogen in some patients with a doc-
umented ischemic vascular disease.
Vorangegangene Untersuchungen haben ein erhöhtes Aggregationsvermögen roter Blutkörperchen bei Patien-
ten mit kardialen und cerebralen Ischämien zeigen können. Mit einer einfachen rheologischen Analysetechnik
wurde in dieser Studie die Erythrozytenadhäsion und -aggregation (EAA) im peripheren Blut von 206 solcher
Patienten untersucht und mit 174 Kontrollpersonen verglichen. Es wurde eine signifikante (p<0.0001) Korrela-
tion zwischen der EAA und der Fibrinogenkonzentration sowie der Blutkörperchensenkungsgeschwindigkeit
(BKS) bei den untersuchten Personen gefunden. Erwähnenswert war ein hochsignifikanter Anstieg der EAA in
einer Untergruppe von 49 Patienten, welche im Vergleich zugesunden Kontrollpersonen normale Fibrino-
genkonzentrationen hatten. Das war auch bei 82 Patienten der Fall, die eine normale BKS aufwiesen. Folglich
scheint die Untersuchung der EAA den Vorteil zu bieten, die Präsenz von adhärenten Akute-Phase-Proteinen
anzuzeigen, welche weder mittels BKS noch anhand einer Fibrinogenbestimmung bei einigen Patienten mit
ischämischen Gefäßerkrankungen festgestellt werden kann.
Des études précédentes ont certifié la présence d'une aggrégabilité accrue des cellules sanguines chez des
patients avec un coeur ischémique et des maladies du cerveau. Nous avons adapté une technique simple de
glissement et d'analyse d'image afin de révéler l'état d'aggrégation/non aggrégation de l'érythrocyte (EAA) dans
le sang périphérique de 206 patients et pour 174 tests. Une corrélation significative (P<0.0001) a été remarquée
entre l'état de l'EAA et les concentrations en fibrinogènes et le taux de sédimentation de l'érythrocyte dans tous
les tests effectués. Plus particulièrement, dans un sous groupe de 49 patients, qui possèdent des concentrations
normales en fibrinogènes, nous avons remarqué une augmentation très significative de l'état de l'EAA par rap-
port à des contrôles saints équivalents. Ce fut également le cas pour 82 patients présentant un taux normal de
sédimentation de l'érythrocyte. Ainsi, le test de l'EAA semble avoir l'avantage de pouvoir détecter la présence
de protéines collantes, qui ne peuvent être révélées par le taux de sédimentation de l'érythrocyte ou par la
présence de fibrinogène coagulant, chez des patients atteints de maladies vasculaires de nature ischémique.
Key words: Erythrocyte aggregation, ischemic vascular disease
Appl. Rheol. 10, 5, 231-237 (2000) September/October 2000
AR • Vol 10 • Nr 5 15.01.2001 16:11 Uhr Seite 232 Table 1 (left): The correlation between the concentration of the hemo- globin and percent of hema- tocrit and either the ery- throcyte sedimentation rate (ESR) or the variables of the test (VR, AR, EP) in 380 patients with ischemic vas- cular diseases and in the controls (VR = vacuum radius, AR = aggregation radius, EP = erythrocyte per- PATIENTS AND METHODS
Table 2 (right): A significant correlation is Previous studies have shown that there is an present between the three increased red blood cell aggregability in patients PATIENTS AND CONTROLS
variables of the erythrocyte with ischemic heart [1-5] and brain[6-9] disease.
Consent was obtained from all the individuals test (EAAT) (VR, AR, EP) and This augmented aggregation might have detri- who participated in the present study according either fibrinogen concentra- mental rheological consequences that lead to to the approval of the local ethics committee.
tion or the erythrocyte sedi- the need for therapeutic interventions for reduc- Included were two groups of patients with ische- mentation rate (ESR) in 380 ing the degree of these cellular interactions.[10- mic vascular diseases and one of healthy controls.
patients and controls. 16]. There are various reasons for the appearance Group assignment was as follows: Figure 1 (bottom): of increased erythrocyte aggregation in patients A typical picture from a with ischemic vascular diseases, among which 1. Ischemic heart disease: patients with chest patient with increased ery- are the presence of an acute phase response and pain who were admitted for observation and throcyte adhesiveness/ag-gregation (left) and a con- an increased synthesis of adhesive proteins, in whom acute myocardial infarction was trol (right). hyperlipidemia, and changes in the erythro- ruled out. Documentation of ischemic heart cyte's membrane. We have recently adapted disease was by means of a history of myocar- a simple slide technique and image analysis to dial infarction (MI), coronary artery bypass reveal the erythrocyte adhesiveness/aggrega- graft surgery (CABG), present or past positive tion state in the peripheral blood.[20-25] The pre- coronary angiography, or a positive thallium sent study was conducted in patients with docu- mented ischemic heart and brain disease. We 2. Ischemic neurological event: patients with an could note the expected significant correlation acute transient ischemic attack or ischemic between the results of this test and either fib- stroke in whom a hemorrhagic stroke was rinogen concentration or the erythrocyte sedi- ruled out by means of computerized tomog- mentation rate. However, an unexpected and significant increment in the EAA state was found 3. Healthy controls: members of the medical in a subgroup of patients who had normal fib- staff and members of a health club who vol- rinogen concentrations and a normal rate of ery- unteered to participate in the study.
throcyte sedimentation, suggesting a potentialadvantage of the erythrocyte adhesive- Excluded from the present study were individuals ness/aggregation test (EAAT) in unmasking rhe- who had any underlying inflammatory or malig- ological information that is not provided by nant disease as well as those who were on either the measurement of clottable fibrinogen steroidal or non-steroidal anti-inflammatory or the erythrocyte sedimentation rate.
medications (except for aspirin up to a dose of 325mg per day). In addition, we excluded individualswho had any traumatic or infectious conditionincluding angiography, surgery or MI during thethree months preceding study recruitment.
VARIABLES OF THE ACUTE PHASE RESPONSE
The blood count was performed by means of theCoulter STKS electronic cell analyzer, the erythro-cyte sedimentation rate by the method of West-ergren  and the concentration of fibrinogenby the method of Clauss  and a Sysmex x6000analyzer.
232 Applied Rheology
September/October 2000 AR • Vol 10 • Nr 5 15.01.2001 16:11 Uhr Seite 233 2.2.2 PREPARATION OF PERIPHERAL BLOOD
to Class 1, which we name Erythrocyte Percent- age (EP). This is the proportion of image area cov- The guidelines for the preparation of the periph- ered by erythrocytes. The two-point statistics are eral blood slides were reported elsewhere. described by the probability p1(r) of a pixel
Briefly, blood was drawn into a syringe contain- belonging to Class 1, given that it is a distance r
ing sodium citrate (one volume of 3.8% sodium from a pixel Class 1, and similarly the probability citrate and three volumes of whole blood). Sev- p2(r) of a pixel belonging to Class 2, given that it
eral large drops of blood were placed on a slide is a distance r from a pixel of Class 2. These prob-
that was held for 2 to 3 seconds at an angle of 45° abilities are equal to 1 for r = 0 and decrease as
so that the blood could run down by gravity, leav- functions of r. As r grows without bound they
ing a fine film. The slides were then dried at room tend to EP and 1-EP, respectively. The typical size temperature while in a completely horizontal of erythrocyte aggregates and of plasma spaces position. Automatic staining was performed by may be quantified by the rate of decrease of the means of the HEMA TEK slide stainer (AMES) and functions p1(r) and p2(r). In the following discus-
a HEMA TEK bloc colorant stain pack (Bayer Diag- sion we will deal with p1, where it is understood that the treatment of p2 is similar. If, for exam-ple, the erythrocyte aggregates are very small, 2.2.3 INFLAMMATION METER (INFLAMET™)
the probability p1(r) will decrease very fast as a
For analysis of the slides, we used an image function of r because at a quite a short distance
analysis system (INFLAMET™) [20-25] consisting from a point of Class 1, a pixel has no longer a of a Pentium Win 95 equipped with a Matrox marked preference to belong to Class 1. A typical Meteor colour frame grabber, a colour CCD cam- distance scale for the size of aggregates may be era and a microscope which was operated at x defined by the negative inverse of the derivative 200 magnification, resulting in an image resolu- of p1 at r = 0. The derivative must be computed
tion of 0.4 micron per pixel. Nine images were numerically, which we did using the following taken from each slide. The fields of view were chosen systematically to sample differentregions on the slide. Each image is processed sep- • Choose a threshold somewhat smaller than 1 arately and the outputs are then averaged to • Find r such as p ) = threshold form the final slide outputs. The nine fields of • Estimate p1'(0) as: view cover a total area of 0.6 mm2.
TION TEST (EAAT)
• The desire distance scale is: The erythrocyte adhesiveness/aggregation statein the peripheral blood was determined by usingthe same image analysis system (INFLAMET™).
We have used color characteristics to classifyimage pixels into two classes: In practice we chose threshold = 0.7 since downto this value p1 appears to be linear. We define Class 1: Aggregates of erythrocytes the aggregation radius (AR) as r0 - differing by a Class 2: Everything else (plasma, platelets, constant factor of 0.3 from above. Vacuum Radius (VR) is the analogous quantity defined forclass 2.
A description of one-point and two-point statis-tics for this classification turns out to require very 2.2.5 STATISTICAL ANALYSIS
few parameters. The main reason for this is that Means ± SD, Student's t-test and the Pearson the image statistics are homogenous (position- coefficient of correlation were carried out by independent) and isotropic (direction-indepen- means of the SPSS package. By using the paired dent). The one point statistics are completely t-test, we compared a subgroup of patients who described by the probability of a pixel belonging had either normal concentrations of fibrinogen September/October 2000 AR • Vol 10 • Nr 5 15.01.2001 16:11 Uhr Seite 234 or a normal erythrocyte sedimentation rate to A significant difference in all healthy controls who presented with exactly the three variables of the ery- same values. Thus, a patient with a fibrinogen ness/aggregation test exists concentration of 292 mg/dL was compared to a between patients with healthy individual with the same value, etc.
ischemic heart and brain disease and the controls despite of their being no dif- ference in the concentration In the present study, we examined a total of 134 of fibrinogen between the patients with an ischemic heart disease (age groups (paired t-test; Hb = hemoglobin, HCT = hemat- 62±13 years; 89 males and 45 females), 72 with an ocrit, ESR = erythrocyte sedi- ischemic neurological event (age 70 ± 12 years; 39 mentation rate, Fg = fib- males and 33 females) and 174 healthy individu- rinogen; all values are given in mean ± SD). als (age 39 ± 17 years, 92 males and 82 females).
The correlation between the three variables ofthe erythrocyte adhesiveness/aggregation test,i.e., the VR, AR and EP, and the hemoglobin con-centration and the hematocrit values in 380 indi-viduals (patients and controls) are shown in Table 1. These correlations were also significant A highly significant differ- when they were applied to the erythrocyte sedi- ence in all three variables of the erythrocyte adhesive- mentation rate (Table 1).
There was a highly significant correla- (EAAT) exists between tion between the three variables of the EAAT and patients with ischemic heart the concentration of fibrinogen as well as the ery- and brain disease and the controls despite of there throcyte sedimentation rate (Table 2). However, being no significant differ- when the results obtained in a subgroup of ence in their erythrocyte patients in whom the concentration of fibrino- gen was found to be within normal limits (i.e.,200-400 mg/dL) were compared to the normalvalues in the controls, significant differences inthe variables of the erythrocyte adhesive-ness/aggregation were observed, despite com-parable fibrinogen concentrations (paired t-test,Table 3). Similar differences could also be seen ina subgroup of patients who had not only com-parable fibrinogen concentrations but also exactly the same erythrocyte sedimentation rate A highly significant differ- (Table 4). In an analysis of a smaller group, we ence exists for all three vari- could reproduce the results and show that this is ables of the erythrocyte not an age-related effect (Table 5).
test (EAAT) between patients with ischemic heart and brain disease and the controls despite of there We adapted a simple slide test coupled with a being no significant differ- precise image analysis system to study the ery- ence in their age, erythro- throcyte adhesiveness/aggregation state in the cyte sedimentation rate or peripheral blood of patients with documented (n.s. = not significant). ischemic heart and brain diseases. As expected,a significant correlation was noted between theadhesiveness/aggregation state and the con-centration of fibrinogen in both the patients andcontrols. In effect, fibrinogen has been shown in 234 Applied Rheology
September/October 2000 AR • Vol 10 • Nr 5 15.01.2001 16:11 Uhr Seite 235 the past to be a major determinant in the appear- correlation between the EAAT and fibrinogen ance of aggregated erythrocytes in the peripher- concentrations that was observed when the al blood  although other acute phase group was evaluated as a whole is suggestive response proteins could participate as well [17, that this molecule does have some role in the 18]. However, our main intent in conducting this induction and on the maintenance of an study was to determine whether the EAAT is increased cell aggregability. The fact that we capable of disclosing information that is not could increase the aggregability of the cells by available by looking at the results of either clot- using an intravenous infusion of gamma globu- table fibrinogen or the sedimentation rate. To do lin  as well as our yet unpublished observa- so, we matched patients and controls who had tions that this aggregability can be attenuated exactly the same within normal limits (200-400 by reducing cholesterol and triglyceride concen- mg/dl) fibrinogen concentrations. It turned out trations in hyperlipidemic individuals, raises the that a clear and significant increment in the EAAT possibility that we are facing a kind of a "sum- values could be seen in the group of patients with marizing" effect of various aggregatory forces ischemic vascular diseases as opposed to the con- that operate on the cells in the peripheral blood trols (Table 3). In a further sub-analysis, we could of a given patient.
show the same results for patients and controls The use of image analysis to detect the who had an identical erythrocyte sedimentation aggregability of red blood cells is not new and has rate: again, a highly significant increment in the been reported in the past . The novel EAAT existed in the patients as opposed to the approach is that we use no dilution or washing controls. Our conclusion is that the direct obser- steps and that the slide test is extremely easy to vation of the aggregated erythrocytes made pos- perform. At the moment we do not know if the sible by using the slide test discloses information aggregation radius and the vacuum radius have that is not demonstrated by either clottable fib- any physiological significance except the idea rinogen concentrations or the erythrocyte sedi- that they give for the typical size of erythrocyte mentation rate in some of the patients.
aggregates and plasma spaces, respectively.
There are multiple causes that can However, we are currently investigating the rela- increase the adhesiveness and aggregation of tions between the morphology of the aggrega- red blood cells in the peripheral blood of patients tion and the inter erythrocytic adhesion forces. It with ischemic vascular disorders, including pro- remains to see whether the most round and cir- teins of the acute phase response [17, 18] hyper- cular aggregates represent the most sticky cells.
lipidemia  and changes in the composition of This might have consequences in terms of flow the erythrocyte membrane [19, 31]. The potential in the microcirculation.
additional diagnostic value of our test is in that The present study was performed in while the above-mentioned factors can acceler- patients with both ischemic heart and brain dis- ate the sedimentation rate, our test was clearly ease. We assume that both have similar etiolo- positive in a group of patients in whom the ery- gies in terms of the presence of atherosclerosis throcyte sedimentation rate was observed as smoldering inflammation as well as similar risk being within normal limits. Thus, our slide test factors. However, we could reproduce the results might be a sensitive test for detecting the pres- in a group of patients with ischemic brain disease ence of a smoldering inflammatory response in solely (to be published elsewhere). Our present a group of individuals with relatively normal fib- study favors, therefore, the notion that the find- rinogen concentrations or erythrocyte sedimen- ings are not confined to a single clinical entity tation rates. Although sensitive CRP assays could and might be related to the underlying patho- be used for this purpose, the importance of directly diagnosing the presence of red blood cell Finally, one has to be aware that various hyperaggregability  lies in the potential ther- optical methodologies have been used to quan- apeutic applications that might result from this titate the aggregability of red blood cells includ- information .
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