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Tissue factor pathway inhibitor in infants and children
Thrombosis Research, Vol. 73, No. 6, pp. 441-446.1994 Copyright 0 1994 Elsetier Science Ltd Printed in the USA. AU rights rescnwl 0049.3848/94 $6.00 + .M)
Pergamon
BRIEF
TISSUE FACTOR PATHWAY
COMMUNICATION
INHIBITOR
IN INFANTS AND CHILDREN
Nils Pargac*, and Kathy Thomas*** Gerhard Weissbach*, Job Harenberg **, Jorg Wendisch*, * Pediatric Clinic of the Medical Academy Dresden, ** Medical Clinic, Faculty of Clinical Medicine Mannheim, University of Heidelberg, and *** Pediatric Clinic of the University of Freiburg, Germany (Received 28 June 1993 by Editor P Kierulf; accepted 23 December
1993)
TFPI, also known as lipoprotein-associated coagulation inhibitor or extrinsic pathway inhibitor forms a complex with factor Xa, which binds to factor VIIa/tissue factor complex and inhibits its catalytic activity (1). Thus TFPI represents a novel control mechanism of blood coagulation. In adults the TFPI plasma level has been evaluated in various disease states. The inhibitor was found to be within normal levels in most patients with hepatocellular diseases and diminished only in the terminal liver failure (1, 2, 3). In septicemia normal to increased levels were observed (4, 5). Increased levels were detected in cases with fatal outcome above all (6). A dramatical increase had been found in patients with postoperative infections (7). In fulminant meningococcal septicemia the inhibitor levels are increased (8). In various states of disseminated intravascular coagulation predominantly normal or elevated levels had been observed (2,3,9). In patients suffenng from malignancies quite different levels were found. But sometimes TFPI was increased (5, 10). In pneumonia (5), in vasculitis and other long term inflammatory disorders (11) normal levels have been reported. A very slow increase of TFPI occurs after surgery , suggesting that it is not an acute phase reactant (12). In contrast to the knowledge on the adult TFPI plasma level, relatively little information is available about the level in infants and in small children. The activity of TFPI in the cord plasma was determined to be 40 to 65 per cent of adult level (5, 13, 14). It is the purpose of the present paper to report on the plasma activity of TFPI in infants and children. MATERIALAND
METHODS
The patient population consisted of 116 infants and children (Table 1), of whom 56 were full-term healthy newborns and 60 were sick infants and children beyond the 7th day of life.For comparison values of a cohort of 45 healthy adults aged 20 - 40 years were used (15). The adult and infant plasma TFPI had been tested in the same laboratory and in the same manner. Collection of the With all patients containing one centrifugation at
samples and probands nine parts of blood from peripheral veins were collected into tubes part of 3.8 % (w/v) tri-sodium citrate solution. Plasma was prepared by 2,500 g for 30 min and stored in 4°C until tested within 4 weeks.
Key words: Tissue factor pathway inhibitor, newborns, children. Abbreviation: TFPI, tissue factor pathway inhibitor Corresponding author: Prof. Dr. G. Weissbach, Pediatric Department Fetscherstr. 74,0-8019 Dresden, Germany
441
of the Medical Academy,
442
TFPI IN INFANTS AND CHILDREN
Vol. 73. No. 6
Test procedure The TFPI was tested on microtiter plates using the assay according to SANDSET et al. (16). Nonactivated purified factors VII and X as well as thromboplastin were from Behringwerke (Marburg, Germany). The residual factor Xa activity was detected using the chromogenic substrate S-2222 (Kabi Stockholm, Sweden). Prior to testing the plasma samples were incubated at 56°C for 15 min to inactivate coagulation factors. The blank values contained the same plasma amounts as the test specimens, because high levels of bilirubin interfere with the assay. The results are expressed in U/ml, whereby one U is defined as the TFPI activity present in 1 ml of normal pooled plasma prepared from 10 healthy adult volunteers. The standard curve was obtained by dilutions of the pooled plasma such that the assay range was from 2 to 0.065 U/ml.
Statistiml an&se3 For all groups and subgroups the following statistical measures were calculated: medians, mean values, variances and standard deviations. The t-test in a special variation was applied to test the difference between mean values. The distribution of the largest groups was tested by the KOLMOGOROV-SMIRNOV line of best fit analyses. The KOLMOGOROV-SMIRNOV 2 sample test and the MANN-WHITNEY U-WILCOXON sum test were used for further analyses of the result distribution. RESULTS As shown in Table 1, the mean value for the healthy newborns (n = 56) was found to be 0.7331 U/ml which according to the t-test analysis is significantly below the mean value obtained for the adults of 0.8270 U/ml (n = 45). The distribution of the TFPI levels was different in the adult and the newborn population ie., according to the KOLMOGOROV-SMIRNOV 2-sample test (p = 0.028) and according to the MANN-WHITNEY U-test (p = 0.016). They can both be accepted for normal distributions. Values of TFPI at various days after birth showed a wide variation, most being below the mean value of the adults (Fi g. 1). A slight tendency toward decreased activities of TFPI could be seen in the first days of life. However this statement cannot be generalised because of the small number of the subgroups studied. After the 6th day the activities of TFPI were not further diminished in healthy infants in comparison to the adults’ standard . even not in preterms.
Table I. Medians (M), Mean Values (a), Standard Deviations (s) and the Results of the Comparison of the Mean Values in the Newborn Group and Subgroups of Infants and Children with the Mean Value in the Cohort of Adults by the modified t-Test.
n
M
x
Healthy adults Healthy newborns
45 56
0.8270 0.7000
0.8719 0.733 1
0.3526 0.2457
0.028
Infants and children beyond the 7th day of life -Tumor and leukemia -Septicemia (inclusive purulent meningitis) -Other inflammatory processes -Hemophilia
60 IO 9
1.2805 1.2513
0.4870 0.1747
0.05 0.01
15 11
1.1842 1.0809
0.4969 0.1660
>0.05 0.01
S
P
Vol. 73, No. 6
TFPI IN INFANTS AND CHILDREN
35
443
0
u/ml 3.G
2.5
2.0
I. 5
I.0
0.5
Values of healthy newborns and infants at different ages. The bold horizontal line characterizes the mean value. The thin lines show the range of the standard deviation in the cohort of adults. The mean values and the standard deviation of some subgroups are marked by brackets. The values of some preterm newborns are given by open circles. During the first week of life most values are located below the adults’ mean value and a slight tendency of decrease cannot be ruled out. Sick infants and children beyond the 7th day of life showed a great variation in the plasma TFPI level (Fig. 2). Patients with tumors and leukemias, with septicemia including purulent meningitis and with other inflammatory diseases predominantly had high plasma TFPI levels, either within or above the upper adults’ range (Table I). Among the patients with septicemia there was one with the Waterhouse-Friderichsen syndrome, whose TFPI activity was 1.450 U/ml a few hours before the fatal outcome. In most patients with hemophilia A and B high values had been observed (Table I). However, markedly elevated levels were found in a in patient with hemophilia A, who recovered from a nephrotic syndrome many months ago and whose total cholesterol level was elevated to 7.66 resp. 9.16 mmol/l at different occasions. The TFPI values from this patient were not used in the statistical analysis. Only a few patients showed levels of TFPI below the adult’s mean value. The lowest value in the tumor subgroup belonged to an infant with malignant histiocytosis. In the group with inflammatory diseases the lowest values belonged to patients with an atypical mycobacteriai infection, with a fetopathy of unclear pathogenesis and with viral encephalitis. DISCUSSION TFPI is an Therefore implications According lower TFPI
important inhibitor, as may be judged from his position in the coagulation system. knowledge about its range in childhood must be of interest, although treatment of bleeding and thrombotic complications cannot be deduced from it at present. to the few previously published data (5, 13, 14) healthy newborns exhibit on average levels than adults . In most cases the values for the newborn population had been in
444
TFPI IN INFANTS AND CHILDREN
Vol. 73, No. 6
u/ml 1.5 0
_-
??
0 1.0
0
0
2
:
_ -______-.__
0.5
r--
6
FIG._. TFPI in infants and children beyond the 7th day of life. The adults’ standard range is given by the horizontal lines. In all the subgroups a considerable variation of the values is the values in a hemophiliac with obvious. The open circles characterize hypercholesterolemia. fact below the mean obtained from a cohort of healthy adults, although some exceptions exist among the newboms.The mechanism for this increase in some newborns is so far not understood. Higher levels could lead to the imagination of a higher degree af maturation of the production capacity. In adults TFPI increases during physical activity, pregnancy and delivery (2, 5, 17). Comparisons of the TFPI activities in the maternal and the newborn plasma would be helpful to explain these observations. However, transfer of maternal TFPI across the placental barrier seems unlikely due to its relatively large molecular mass. TFPI had been reported to have a molecular mass of 33 kDa and up to 40 kDa when complexed with low and possibly with high density lipoproteins (1, 5, 9). Comparisons of the TFPI level with the concentration of other plasma proteins and with the lipoprotein spectrum may offer a helpful explanation. The proportion of the TFPI level which is expressed during the amidolytic assay by the free and the lipoprotein-bound protein is not known. Fractionation of the TFPI activity as well as simultaneous detection by clotting and amidolytic assays would be of interest (9), because different aspects may be measured by tests of different specificities. The observed tendency of decreasing TFPI activity during the first days of life cannot be generalised from our data. A larger group would be needed to confirm these results. In healthy infants beyond the 6th day of fife values within the adults’ standard range can be expected.
Vol. 73, No. 6
TFPI IN INFANTS AND CHILDREN
445
In sick infants and children beyond the 7th day of life a wide variation of the TFPI activity was noted, similar to that observed for adults. In some patients with malignant diseases and septicemia TFPI behaved like an acute phase reactant, but with a weak reactivity. This first impression should be confirmed by investigation series because in adult patients it was not always seen. In fulminant meningococcal disease increasing levels had been observed, especially in patients with a fatal outcome ( 11) and the high value seen in the patient with Waterhouse - Friderichsen syndrome is in agreement with these observations. An increased expression of TFPI by inflammatory agents was demonstrated also in the endothelial cell culture (4). The TFPI activity is sensitive to the leucocyte-derived elastase which is likely to be released in the course of bacteremic and other inflammatory disorders (18). The destruction of TFPI by elastase could thus account for the The increased activity could be caused by the relatively low levels seen in some patients. occurrence of fractions with a higher activity (19). In vitro, the TFPI has been shown to be more efficacious in the absence of the coagulation factors VIII and IX (20,21). It is therefore of interest to note that the level of TFPI was elevated in some patients with hemophilia A and B. Replacement therapy with factor concentrates is unlikely to be the cause for the elevation in these patients since other hemophiliacs had lower TFPI levels in spite of replacement therapy. The cholesterol level was increased at the time of blood sampling in the hemophiliac with the highest TFPI values. Such elevation of TFPI may be caused by the abnormal lipoprotein profile more likely than by the coagulation defect. In adults the close correlation between TFPI and cholesterol levels is well known (14). TFPI seems to react in a similar manner in children as in adults despite of its lower activity during the first days of life. REFERENCES 1. RAPAPORT, S. I. The extrinsic pathway inhibitor: A regulator of tissue factor-dependent blood coagulation. Thromb Haemost 66,6 - 15, 1991. 2. NOVOTNY, W. F., BROWN, S. G., MILETICH, J. P., RADER. D. J. and BROZE, G. J. JR. Plasma antigen levels of the lipoprotein-associated coagulation inhibitor in patient samples. Blood 78,387 - 393, 1991. 3. WARR, T. A., RAO, L. V .M. and RAPAPORT, S. I. Human plasma extrinsic pathway inhibitor activity: II. Plasma levels in disseminated intravascular coagulation and hepatocellular disease. Blood 74,994 - 998, 1989. 4. AMERI, A., KUPPUSWAMY, M. N., BASU, S., HOYER, M. A. and BAJAJ, S. P. Modulation of tissue factor and EPI I LACI expression by cultured endothelial cells in response to inflammatory agents (Abstr.). Thromb Haemost 65,701, 1991. 5. SANDSET, P. M. and ABILDGAARD, U. Extrinsic pathway inhibitor- The key to feedback control of blood coagulation initiated by tissue thromboplastin. Haemostasis 21,219 - 239, 1991. 6. SANDSET, P. M., ROISE, O., AASEN, A. 0. and ABILDGAARD, U. Extrinsic pathway inhibitor in postoperative / posttraumatic septicemia: Increased levels in fatal cases. Haemostasis 19, 189 - 195, 1989. 7. CARSON, S. D., HAIRE, W. D., BROZE, G. J. JR., NOVOTNY, W. F., PIRRUCELLO, S. J. and DUGGAN, M. J. Lipoprotein associated coagulation inhibitor, factor VII, antithrombin III, and monocyte tissue factor following surgery. Thromb Haemost 66,534 - 539, 1991. 8. BRANDTZAEG, P., SANDSET, P. M., JO0, G. B., 0VSTEB0, R., ABILDGAARD, U. and KIERULF, P. The quantitative association of plasma endotoxin, antithrombin, protein C, extrinsic pathway inhibitor and fibrinopeptide A in systemic meningococcal disease. Thrombosis Res 55,459 - 470, 1989. 9. LINDAHL, A. K., SANDSET, P. M. and ABILDGAARD, U. The present status of tissue factor pathway inhibitor. Blood Coag Rbrinol 3,439 - 449, 1992 10. LINDAHL. A. K.. SANDSET. P. M.. HARBITZ. T.. ANDERSSON. T. and ABILDGAARD, U. Coagulation inhibitors in patients with advanced cancer disease. Acta Chir Stand 155.389 - 393. 1989. 11. BRADSHAW, A.’E., KELLY, S. M. and BEYNON, H. Extrinsic pathway inhibitor levels in patients with vasculitis (Abstr.). Thromb Haemost 65 ,949, 1991. 12. SANDSET, P. M., HOGEVOLD, H. E., LYBERG, T., ANDERSSON, T. R. and ABILDGAARD, U. Extrinsic pathway inhibitor in elective surgery: A comparison with other coagulation inhibitors. Thromb Haemost 62,856 - 860, 1989.
446
TFPI IN INFANTS AND CHILDREN
Vol. 73, No. 6
13. WARR, T. A., WARN-CRAMER, B. J., RAO, L. V. M. and RAPAPORT, S. I. Human plasma extrinsic pathway inhibitor activity: I. Standardization of assay and evaluation of physiologic variables. Blood 74,201 - 206, 1989. 14. SANDSET, P. M., LARSEN, M. L., ABILDGAARD, U., LINDAHL, A. K. and ODEGAARD, 0. R. Chromogenic substrate assay of extrinsic pathway inhibitor (EPI): Levels in the normal population and relation to cholesterol. Blood Coag Fibrin01 2,425 - 433, 1991. 15. HARENBERG, J., SCHAFER, M., STEHLE, G., SCHMIDT, M., DEMPFLE, C. E. and HEENE, D.L. Release of the extrinsic pathway inhibitor, hepatic lipase and anti-factor Xa activity into post-heparin plasma (Abstr.). Thromb Haemost 65,952, 1991. 16. SANDSET, P. M., ABILDGAARD, U. and PETTERSEN, M. A sensitive assay of extrinsic coagulation pathway inhibitor in plasma and plasma fractions. Thrombosis Res 47,389 - 400, 1987. 17. HANSEN, J. B., OLSEN, J.-O. and OSTERUD, B. Physical exercise enhances plasma levels of extrinsic pathway inhibitor (EPI). Thromb Haemost 64, 124 - 126, 1990. 18. HIGUCHI, D. A., WUN, T.-C., LIKERT, K. M. and BROZE, G. J. JR. The effect of leukocyte elastase on tissue factor pathway inhibitor. Blood 79, 1712 - 1719, 1992. 19. LINDAHL, A. K., JACOBSEN, P. B., SANDSET, P. M. and ABILDGAARD, U. Tissue factor pathway inhibitor with high anticoagulant activity is increased in post-heparin plasma and in plasma from cancer patients. Blood Coag Fibrin01 2,713 - 721, 1991. 20. NORDFANG, O., VALENTIN, S., BECK, T. C. and HEDNER, U. Inhibition of extrinsic pathway inhibitor shortens the coagulation time of normal plasma and of hemophilia plasma. Thromb Haemost 66,464 - 467, 1991. 21. VALENTIN, S., OSTERGAARD, P., KRISTENSEN, H. and NORDFANG, 0. Simultaneous presence of tissue factor pathway inhibitor (TFPI) and low molecular weight heparin has a synergistic effect in different coagulation assays. Blood Coag Fibrin01 2.629 - 635, 1991.
Pergamon
BRIEF
TISSUE FACTOR PATHWAY
COMMUNICATION
INHIBITOR
IN INFANTS AND CHILDREN
Nils Pargac*, and Kathy Thomas*** Gerhard Weissbach*, Job Harenberg **, Jorg Wendisch*, * Pediatric Clinic of the Medical Academy Dresden, ** Medical Clinic, Faculty of Clinical Medicine Mannheim, University of Heidelberg, and *** Pediatric Clinic of the University of Freiburg, Germany (Received 28 June 1993 by Editor P Kierulf; accepted 23 December
1993)
TFPI, also known as lipoprotein-associated coagulation inhibitor or extrinsic pathway inhibitor forms a complex with factor Xa, which binds to factor VIIa/tissue factor complex and inhibits its catalytic activity (1). Thus TFPI represents a novel control mechanism of blood coagulation. In adults the TFPI plasma level has been evaluated in various disease states. The inhibitor was found to be within normal levels in most patients with hepatocellular diseases and diminished only in the terminal liver failure (1, 2, 3). In septicemia normal to increased levels were observed (4, 5). Increased levels were detected in cases with fatal outcome above all (6). A dramatical increase had been found in patients with postoperative infections (7). In fulminant meningococcal septicemia the inhibitor levels are increased (8). In various states of disseminated intravascular coagulation predominantly normal or elevated levels had been observed (2,3,9). In patients suffenng from malignancies quite different levels were found. But sometimes TFPI was increased (5, 10). In pneumonia (5), in vasculitis and other long term inflammatory disorders (11) normal levels have been reported. A very slow increase of TFPI occurs after surgery , suggesting that it is not an acute phase reactant (12). In contrast to the knowledge on the adult TFPI plasma level, relatively little information is available about the level in infants and in small children. The activity of TFPI in the cord plasma was determined to be 40 to 65 per cent of adult level (5, 13, 14). It is the purpose of the present paper to report on the plasma activity of TFPI in infants and children. MATERIALAND
METHODS
The patient population consisted of 116 infants and children (Table 1), of whom 56 were full-term healthy newborns and 60 were sick infants and children beyond the 7th day of life.For comparison values of a cohort of 45 healthy adults aged 20 - 40 years were used (15). The adult and infant plasma TFPI had been tested in the same laboratory and in the same manner. Collection of the With all patients containing one centrifugation at
samples and probands nine parts of blood from peripheral veins were collected into tubes part of 3.8 % (w/v) tri-sodium citrate solution. Plasma was prepared by 2,500 g for 30 min and stored in 4°C until tested within 4 weeks.
Key words: Tissue factor pathway inhibitor, newborns, children. Abbreviation: TFPI, tissue factor pathway inhibitor Corresponding author: Prof. Dr. G. Weissbach, Pediatric Department Fetscherstr. 74,0-8019 Dresden, Germany
441
of the Medical Academy,
442
TFPI IN INFANTS AND CHILDREN
Vol. 73. No. 6
Test procedure The TFPI was tested on microtiter plates using the assay according to SANDSET et al. (16). Nonactivated purified factors VII and X as well as thromboplastin were from Behringwerke (Marburg, Germany). The residual factor Xa activity was detected using the chromogenic substrate S-2222 (Kabi Stockholm, Sweden). Prior to testing the plasma samples were incubated at 56°C for 15 min to inactivate coagulation factors. The blank values contained the same plasma amounts as the test specimens, because high levels of bilirubin interfere with the assay. The results are expressed in U/ml, whereby one U is defined as the TFPI activity present in 1 ml of normal pooled plasma prepared from 10 healthy adult volunteers. The standard curve was obtained by dilutions of the pooled plasma such that the assay range was from 2 to 0.065 U/ml.
Statistiml an&se3 For all groups and subgroups the following statistical measures were calculated: medians, mean values, variances and standard deviations. The t-test in a special variation was applied to test the difference between mean values. The distribution of the largest groups was tested by the KOLMOGOROV-SMIRNOV line of best fit analyses. The KOLMOGOROV-SMIRNOV 2 sample test and the MANN-WHITNEY U-WILCOXON sum test were used for further analyses of the result distribution. RESULTS As shown in Table 1, the mean value for the healthy newborns (n = 56) was found to be 0.7331 U/ml which according to the t-test analysis is significantly below the mean value obtained for the adults of 0.8270 U/ml (n = 45). The distribution of the TFPI levels was different in the adult and the newborn population ie., according to the KOLMOGOROV-SMIRNOV 2-sample test (p = 0.028) and according to the MANN-WHITNEY U-test (p = 0.016). They can both be accepted for normal distributions. Values of TFPI at various days after birth showed a wide variation, most being below the mean value of the adults (Fi g. 1). A slight tendency toward decreased activities of TFPI could be seen in the first days of life. However this statement cannot be generalised because of the small number of the subgroups studied. After the 6th day the activities of TFPI were not further diminished in healthy infants in comparison to the adults’ standard . even not in preterms.
Table I. Medians (M), Mean Values (a), Standard Deviations (s) and the Results of the Comparison of the Mean Values in the Newborn Group and Subgroups of Infants and Children with the Mean Value in the Cohort of Adults by the modified t-Test.
n
M
x
Healthy adults Healthy newborns
45 56
0.8270 0.7000
0.8719 0.733 1
0.3526 0.2457
0.028
Infants and children beyond the 7th day of life -Tumor and leukemia -Septicemia (inclusive purulent meningitis) -Other inflammatory processes -Hemophilia
60 IO 9
1.2805 1.2513
0.4870 0.1747
0.05 0.01
15 11
1.1842 1.0809
0.4969 0.1660
>0.05 0.01
S
P
Vol. 73, No. 6
TFPI IN INFANTS AND CHILDREN
35
443
0
u/ml 3.G
2.5
2.0
I. 5
I.0
0.5
Values of healthy newborns and infants at different ages. The bold horizontal line characterizes the mean value. The thin lines show the range of the standard deviation in the cohort of adults. The mean values and the standard deviation of some subgroups are marked by brackets. The values of some preterm newborns are given by open circles. During the first week of life most values are located below the adults’ mean value and a slight tendency of decrease cannot be ruled out. Sick infants and children beyond the 7th day of life showed a great variation in the plasma TFPI level (Fig. 2). Patients with tumors and leukemias, with septicemia including purulent meningitis and with other inflammatory diseases predominantly had high plasma TFPI levels, either within or above the upper adults’ range (Table I). Among the patients with septicemia there was one with the Waterhouse-Friderichsen syndrome, whose TFPI activity was 1.450 U/ml a few hours before the fatal outcome. In most patients with hemophilia A and B high values had been observed (Table I). However, markedly elevated levels were found in a in patient with hemophilia A, who recovered from a nephrotic syndrome many months ago and whose total cholesterol level was elevated to 7.66 resp. 9.16 mmol/l at different occasions. The TFPI values from this patient were not used in the statistical analysis. Only a few patients showed levels of TFPI below the adult’s mean value. The lowest value in the tumor subgroup belonged to an infant with malignant histiocytosis. In the group with inflammatory diseases the lowest values belonged to patients with an atypical mycobacteriai infection, with a fetopathy of unclear pathogenesis and with viral encephalitis. DISCUSSION TFPI is an Therefore implications According lower TFPI
important inhibitor, as may be judged from his position in the coagulation system. knowledge about its range in childhood must be of interest, although treatment of bleeding and thrombotic complications cannot be deduced from it at present. to the few previously published data (5, 13, 14) healthy newborns exhibit on average levels than adults . In most cases the values for the newborn population had been in
444
TFPI IN INFANTS AND CHILDREN
Vol. 73, No. 6
u/ml 1.5 0
_-
??
0 1.0
0
0
2
:
_ -______-.__
0.5
r--
6
FIG._. TFPI in infants and children beyond the 7th day of life. The adults’ standard range is given by the horizontal lines. In all the subgroups a considerable variation of the values is the values in a hemophiliac with obvious. The open circles characterize hypercholesterolemia. fact below the mean obtained from a cohort of healthy adults, although some exceptions exist among the newboms.The mechanism for this increase in some newborns is so far not understood. Higher levels could lead to the imagination of a higher degree af maturation of the production capacity. In adults TFPI increases during physical activity, pregnancy and delivery (2, 5, 17). Comparisons of the TFPI activities in the maternal and the newborn plasma would be helpful to explain these observations. However, transfer of maternal TFPI across the placental barrier seems unlikely due to its relatively large molecular mass. TFPI had been reported to have a molecular mass of 33 kDa and up to 40 kDa when complexed with low and possibly with high density lipoproteins (1, 5, 9). Comparisons of the TFPI level with the concentration of other plasma proteins and with the lipoprotein spectrum may offer a helpful explanation. The proportion of the TFPI level which is expressed during the amidolytic assay by the free and the lipoprotein-bound protein is not known. Fractionation of the TFPI activity as well as simultaneous detection by clotting and amidolytic assays would be of interest (9), because different aspects may be measured by tests of different specificities. The observed tendency of decreasing TFPI activity during the first days of life cannot be generalised from our data. A larger group would be needed to confirm these results. In healthy infants beyond the 6th day of fife values within the adults’ standard range can be expected.
Vol. 73, No. 6
TFPI IN INFANTS AND CHILDREN
445
In sick infants and children beyond the 7th day of life a wide variation of the TFPI activity was noted, similar to that observed for adults. In some patients with malignant diseases and septicemia TFPI behaved like an acute phase reactant, but with a weak reactivity. This first impression should be confirmed by investigation series because in adult patients it was not always seen. In fulminant meningococcal disease increasing levels had been observed, especially in patients with a fatal outcome ( 11) and the high value seen in the patient with Waterhouse - Friderichsen syndrome is in agreement with these observations. An increased expression of TFPI by inflammatory agents was demonstrated also in the endothelial cell culture (4). The TFPI activity is sensitive to the leucocyte-derived elastase which is likely to be released in the course of bacteremic and other inflammatory disorders (18). The destruction of TFPI by elastase could thus account for the The increased activity could be caused by the relatively low levels seen in some patients. occurrence of fractions with a higher activity (19). In vitro, the TFPI has been shown to be more efficacious in the absence of the coagulation factors VIII and IX (20,21). It is therefore of interest to note that the level of TFPI was elevated in some patients with hemophilia A and B. Replacement therapy with factor concentrates is unlikely to be the cause for the elevation in these patients since other hemophiliacs had lower TFPI levels in spite of replacement therapy. The cholesterol level was increased at the time of blood sampling in the hemophiliac with the highest TFPI values. Such elevation of TFPI may be caused by the abnormal lipoprotein profile more likely than by the coagulation defect. In adults the close correlation between TFPI and cholesterol levels is well known (14). TFPI seems to react in a similar manner in children as in adults despite of its lower activity during the first days of life. REFERENCES 1. RAPAPORT, S. I. The extrinsic pathway inhibitor: A regulator of tissue factor-dependent blood coagulation. Thromb Haemost 66,6 - 15, 1991. 2. NOVOTNY, W. F., BROWN, S. G., MILETICH, J. P., RADER. D. J. and BROZE, G. J. JR. Plasma antigen levels of the lipoprotein-associated coagulation inhibitor in patient samples. Blood 78,387 - 393, 1991. 3. WARR, T. A., RAO, L. V .M. and RAPAPORT, S. I. Human plasma extrinsic pathway inhibitor activity: II. Plasma levels in disseminated intravascular coagulation and hepatocellular disease. Blood 74,994 - 998, 1989. 4. AMERI, A., KUPPUSWAMY, M. N., BASU, S., HOYER, M. A. and BAJAJ, S. P. Modulation of tissue factor and EPI I LACI expression by cultured endothelial cells in response to inflammatory agents (Abstr.). Thromb Haemost 65,701, 1991. 5. SANDSET, P. M. and ABILDGAARD, U. Extrinsic pathway inhibitor- The key to feedback control of blood coagulation initiated by tissue thromboplastin. Haemostasis 21,219 - 239, 1991. 6. SANDSET, P. M., ROISE, O., AASEN, A. 0. and ABILDGAARD, U. Extrinsic pathway inhibitor in postoperative / posttraumatic septicemia: Increased levels in fatal cases. Haemostasis 19, 189 - 195, 1989. 7. CARSON, S. D., HAIRE, W. D., BROZE, G. J. JR., NOVOTNY, W. F., PIRRUCELLO, S. J. and DUGGAN, M. J. Lipoprotein associated coagulation inhibitor, factor VII, antithrombin III, and monocyte tissue factor following surgery. Thromb Haemost 66,534 - 539, 1991. 8. BRANDTZAEG, P., SANDSET, P. M., JO0, G. B., 0VSTEB0, R., ABILDGAARD, U. and KIERULF, P. The quantitative association of plasma endotoxin, antithrombin, protein C, extrinsic pathway inhibitor and fibrinopeptide A in systemic meningococcal disease. Thrombosis Res 55,459 - 470, 1989. 9. LINDAHL, A. K., SANDSET, P. M. and ABILDGAARD, U. The present status of tissue factor pathway inhibitor. Blood Coag Rbrinol 3,439 - 449, 1992 10. LINDAHL. A. K.. SANDSET. P. M.. HARBITZ. T.. ANDERSSON. T. and ABILDGAARD, U. Coagulation inhibitors in patients with advanced cancer disease. Acta Chir Stand 155.389 - 393. 1989. 11. BRADSHAW, A.’E., KELLY, S. M. and BEYNON, H. Extrinsic pathway inhibitor levels in patients with vasculitis (Abstr.). Thromb Haemost 65 ,949, 1991. 12. SANDSET, P. M., HOGEVOLD, H. E., LYBERG, T., ANDERSSON, T. R. and ABILDGAARD, U. Extrinsic pathway inhibitor in elective surgery: A comparison with other coagulation inhibitors. Thromb Haemost 62,856 - 860, 1989.
446
TFPI IN INFANTS AND CHILDREN
Vol. 73, No. 6
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