Determination of an individual's inflammation index from whole blood fibrinogen and hematocrit or hemoglobin measurements

Useful information about a subject's level of systemic inflammation is obtained by quantitatively measuring the amount of fibrinogen and the hematocrit and or hemoglobin in the subject's whole blood. The fibrinogen measurement, when combined with an hematocrit or hemoglobin measurement, provides a systemic Inflammation Index value for the donor. The method is not affected by blood variables which are not related to the presence of inflammation, which blood variables are known to invalidate an erythrocyte sedimentation rate, which is the most frequently used blood test for detecting systemic inflammation in humans.

TECHNICAL FIELD 
This invention relates to a method for determining the presence or absence 
of an inflammatory condition in an individual by quantifying both the 
fibrinogen content and the hematocrit or hemoglobin in a sample of the 
individual's blood, and calculating a composite Inflammation Index for the 
individual which is derived from the aforesaid two variables. 
BACKGROUND ART 
Inflammation is a basic pathophysiologic process that is defined as the 
reaction of vascularized living tissue to local injury. The inflammatory 
process is important to the host because it serves in the process of 
repair of the injury and destruction of pathogenic organisms and tumors 
but sometimes inflammation may be harmful when it continues unchecked, as 
in rheumatoid arthritis. The detection of the inflammatory process is 
important to physicians because it indicates the presence of significant 
illness or injury. Examples of illnesses often characterized by 
significant inflammation are myocardial infarction, active tuberculosis, 
osteomyelitis (bone infection), rheumatoid arthritis, cholecytistis 
(infected gall bladder), and pyelonephritis (infected kidney), and 
disseminated cancer among others. 
Patients who have significant inflammatory processes often have signs and 
symptoms of inflammation that are well known, such as fever, fatigue, loss 
of appetite, low blood pressure, and sometimes abnormalities in the amount 
of circulating white blood cells including both elevation and depression 
of their numbers, but these signs and symptoms are neither sensitive nor 
specific to the presence of inflammation. Many diseases and physical 
conditions, such as those listed above will cause inflammatory responses 
which can be noted in the blood. These inflammatory responses can 
frequently occur before more specific signs and symptoms of disease can be 
identified, and thus the detection of the presence of inflammation may 
allow more prompt diagnosis and treatment of the underlying condition. The 
best known and most widely used blood test indicator of inflammation is 
the erythrocyte sedimentation rate or ESR. The ESR was discovered by 
Fahraeus and popularized and improved by Wintrobe and Westergren. The 
Westergren erythrocyte sedimentation rate, or Westergren ESR, or WESR, 
which is sensitive to global elevations in inflammatory proteins is 
performed by measuring the distance the erythrocytes have sedimented in 60 
minutes in a sample of anticoagulated blood which has been placed in a 200 
mm long tube of defined dimensions. It has been an enduring laboratory 
test for both screening patients on an initial visit to a physician, and 
for following the evolution of the inflammatory condition in return 
visits. Despite the widespread use of the ESR procedure, there are certain 
drawbacks to this test which relate to, among other things, the amount of 
blood used to perform the test (at least one milliliter, which is a large 
amount for an infant); the amount of time needed to perform the test (one 
hour), and the fact that the test should optimally be performed within two 
hours of obtaining the blood. The ESR performed in the manner described by 
Wintrobe and Westergren is also affected by factors that may not indicate 
the presence or absence of inflammation such as: the presence of 
abnormally shaped red cells; the presence of proteins affecting the 
viscosity of the blood; the presence of antibody or cold agglutinens 
directed against red blood cells; the general level of gamma globulins 
even if they are not directed against the red cells; and deviations from 
verticality of the ESR tube while the test is being performed, as well as 
ambient temperature and vibration. Physicians therefore have attempted to 
develop other tests for inflammation that may be easier or quicker, or 
more sensitive or specific. Such tests include the C reactive protein or 
CRP; the white blood cell count; the granulocyte count (a component of the 
white blood cell count); the orosomucoid protein; the hematocrit or 
hemoglobin; and the fibrinogen. A total of at least sixteen tests have 
been used to monitor inflammation. All of these tests have advantages, as 
well as disadvantages, but none of them have been shown to be superior to 
the ESR. 
It would be highly desirable to have a procedure for ascertaining the level 
of systemic inflammation; and which procedure requires only a small sample 
of blood; and which procedure can be relatively quickly performed or which 
procedure may be performed after a period of several hours if necessary; 
and which procedure is not adversely affected by abnormal blood conditions 
that skew the results of the ESR. 
DISCLOSURE OF THE INVENTION 
A technique exists for the ranking of the utility of laboratory tests 
called "consensus analysis". This technique, conceived by Bull and others 
based in part on the work of Spearman, and modernized by Bull, is able to 
discern the most effective test, or most effective weighted combination of 
tests, to detect a given condition. The technique of "concensus analysis" 
is described in an article by Bull et al entitled "Ranking of Laboratory 
Tests by Consensus Analysis", published Aug. 16, 1986 in The Lancet. Using 
consensus analysis, the ESR has proven itself the best single performer 
among the sixteen tests now used to monitor rheumatology patients. Since a 
major contributor to the ESR is known to be the fibrinogen level, and the 
hematocrit or hemoglobin are known to be decreased in inflammatory 
conditions, we have applied consensus analysis to ascertain if these 
determinations, which may be performed more rapidly and on smaller volumes 
of blood, would, if combined in a composite, yield information clinically 
equivalent to, or better than that provided by the widely used ESR. 
We have found, using the tools of consensus analysis, and the results of 
analyses of blood samples taken from a group of one hundred patients who 
had demonstrated a wide range of indicators of inflammation, that a 
combination of the WESR, fibrinogen and the CRP, which combination we have 
dubbed "the composite index", was the best indicator of the presence of 
systemic patient inflammation. 
Because the composite index consists of tests that cannot be easily or 
rapidly performed, it does not possess significant clinical utility We 
found, however, that a composite result procedure involving fibrinogen 
measurements and hematocrit or hemoglobin measurements (the "Inflammation 
Index") provides information about the extent of inflammation which 
closely conforms to the results from the composite index, and is in closer 
conformity to the composite index results than are the results obtained 
from the WESR alone. 
The Inflammation Index, in humans, using the fibrinogen measurement 
expressed in mg/dl, and the hematocrit (Hct) measurement as a volume 
percent of the packed red cells in the blood sample, was determined by us 
to be equal to: 
EQU 0.154 (fibrinogen)-1.667(Hct)+42. 
For example, a patient without significant clinical inflammation and a 
fibrinogen level of 200 mg/dl with an hematocrit of 42% would result in an 
Inflammation Index as follows: 
EQU 0.154(200)-1.667(42.0)+42.apprxeq.3 
A patient with a high level of systemic inflammation and a fibrinogen level 
of 800 mg/dl with an hematocrit of 28.0% would result in an Inflammation 
Index as follows: 
EQU 0.154(800)-1.667(28.0)+42.apprxeq.118 
If hemoglobin values are used, expressed in gm/dl the constant -1.667 will 
be -5.001. The other constants will remain the same. 
Thus the general equation for determining a donor's inflammation index is: 
I=a(f)+b(h)+c; wherein "I" is the inflammation index; "f" is the 
fibrinogen level in the blood sample; "h" is the hematocrit or hemoglobin 
value in the blood sample; and "a", "b", and "c" are empirically derived 
constants. 
For human blood, the empirical constants were derived by comparing the 
consensus analysis of human blood ESR analysis, human blood fibrinogen 
analysis, and human blood CRP analysis from a donor population of 100 
patients displaying a wide range of inflammation indicators, with the 
fibrinogen/fibrin level and a hematocrit or hemoglobin determination 
combination from the same donor population. 
If a non-human mammalian blood sample, as for example animal blood, were 
being analyzed, then different constants would be required, and a parallel 
consensus analysis determination would have to be made to determine such 
constants. 
It should be noted that the Inflammation Index value, being a composite 
number, has no dimensions or units, and that the range of values resulting 
from the test is similar to the range of values of the WESR. The 
Inflammation Index results obtained by performing the method of this 
invention can therefore be easily interpreted by physicians with the 
numerical result being approximately comparable to a WESR without being 
adversely affected by the factors previously mentioned and with the added 
reliability inherent in the composite number. 
A simple and quick procedure for quantifying the fibrinogen content in an 
anticoagulated whole blood sample is described in U.S. Pat. No. 5,137,832, 
granted Aug. 11, 1992 to R. A. Levine et al. The aforesaid procedure may 
be performed in a physician's office in a matter of about fifteen minutes, 
or so. The paraphernalia used to perform the aforesaid fibrinogen 
quantification includes a blood sampling tube of precise volume, and a 
float which is positioned in the tube. A layer of precipitated fibrinogen 
and/or fibrin settles on the top of the float after centrifugation of the 
sample in the tube. A computerized instrument which measures the linear 
length of the fibrinogen and/or fibrin layer in the tube as well as the 
length of the total sample in the tube, is used to convert the fibrinogen 
linear layer measurement to a quantification of the amount of fibrinogen 
and/or fibrin in the sample. The same paraphernalia can also be used to 
measure a patient's hematocrit and hemoglobin as described in U.S. Pat. 
No. 4,843,869, granted Jul. 4, 1989 to R. A. Levine et al. By combining 
fibrinogen level information with information about the hematocrit or 
hemoglobin level in the blood, as described above, one can derive an 
Inflammation Index value for the patient The fibrinogen-hematocrit or 
hemoglobin values, and thus the Inflammation Index value, can be 
determined much more rapidly than the WESR and/or the CRP and the amount 
of blood required to perform the method is about one-tenth that needed for 
the WESR. In addition, and most importantly, the results will not be 
skewed by systemic abnormalities that render the WESR inaccurate. 
It is therefore an object of this invention to provide a procedure for 
providing an Inflammation Index value for a blood sample, which index is 
indicative of systemic inflammation in the donor of the blood sample. 
It is a further object of this invention to provide a procedure of the 
character described which is not susceptible to systemic abnormalities 
that render the WESR unreliable. 
It is an additional object of this invention to provide a procedure of the 
character described wherein the level of fibrinogen and/or fibrin is 
quantified, and is combined with an hematocrit or hemoglobin 
quantification in the blood sample in order to ascertain a measure of 
systemic inflammation. 
It is yet another object of this invention to provide a procedure of the 
character described wherein the amount of blood needed for the procedure 
is small and the time needed to perform the procedure is short.

SPECIFIC EMBODIMENT OF THE INVENTION 
Referring now to FIG. 1, there is shown a blood sampling tube which is 
denoted generally by the numeral 2. The tube 2 is typically a capillary 
tube and it contains an elongated plastic insert or float 4 which is 
formed from a plastic which has a specific gravity that results in the 
insert 4 settling into and floating on a layer 8 of packed red blood cells 
8 that settle into the bottom of the tube 2 when the tube 2 and insert 4 
are centrifuged with a sample of anticoagulated whole blood contained in 
the tube 2. The bottom of the tube 2 is closed with a plastic cap 6 or the 
like. When the tube 2, insert 4 and blood sample are processed as 
described in the aforesaid U.S. Pat. No. 5,137,832, the specification of 
which is incorporated herein in its entirety for purposes of enablement, 
and centrifuged, the blood sample constituents will settle out in 
different layers as shown in the drawing. The red cells will settle into 
the lowermost portion of the tube 2 in a layer 8. The insert 4 will settle 
into the red cell layer 8 and float therein. The insert 4 will project 
upwardly through the white cell/platelet, or buffy coat layer 12 into the 
plasma layer, which is the uppermost layer of the sample. The precipitated 
fibrinogen and/or fibrin in the blood sample will settle into a band 10 
which ends up on the top of the insert 4 and in the plasma layer. The 
length of the red cell layer 8 is measured by a preprogrammed 
microprocessor-operated instrument such as those disclosed in U.S. Pat. 
Nos. 4,156,570, granted May 29, 1979; 4,558,947, granted Dec. 17, 1985; 
and 4,683,579, granted Jul. 28, 1987, all to S. C. Wardlaw. Instruments of 
the type disclosed in the latter two patents are sold by Becton Dickinson 
and Company under the trademark QBC AUTOREADER.RTM.. The red blood cell 
layer measurement along with a measurement of the length of entire blood 
sample 14 as taken from the miniscus 13 at the top of the plasma layer to 
the closure cap 6 will provide the hematocrit value for the blood sample. 
When calculating the hematocrit, the instrument will correct for the fact 
that the insert extends a short distance into the red cell layer 8. The 
instrument is also used to measure the linear extent of the 
fibrinogen/fibrin layer 10 and convert that measurement into a fibrinogen 
count. The instrument will then use the hematocrit value and the 
fibrinogen/fibrin value to calculate the Inflammation Index by making the 
calculation specified above. When the Inflammation Index has been 
determined, its value will be displayed or printed out by the instrument 
for the physician. 
It will be readily appreciated that the determination of systemic 
inflammation by using the procedure of this invention can be performed 
with a minimal amount of blood, and in a minimum amount of time. The 
procedure of this invention is essentially immune to factors, both 
biological and procedural, which will produce inaccurate results when 
using the WESR procedure to determine the extent of systemic inflammation. 
While the aforesaid description of the invention has been specifically 
directed to the determination of an Inflammation Index for humans, the 
invention can also be used to determine an Inflammation Index for other 
mammalian species, and thus can be used in the measurement of inflammation 
in animals in the practice of veterinary medicine. Naturally, different 
multipliers of the hematocrit and fibrinogen/fibrin measurements and 
different constants will have to be determined for different animal 
species. 
Since many changes and variations in the disclosed embodiments of the 
invention may be made without departing from the inventive concept, it is 
not intended to limit the invention otherwise than as required by the 
appended claims.