Behaviour of commercially prepared I-125 fibrinogen in metabolic studies

Haptoglobin in Juvenile Idiopathic Arthritis

BACKGROUND

Haptoglobin (Hp), a liver derived acute phase inflammatory protein (APP), has scarcely been studied in juvenile idiopathic arthritis (JIA). Hp can occur in blood as two isoforms (Hp1 and Hp2) in precursor and mature forms. Routine clinical chemistry immunoturbidimetry does not discern these forms. It is unknown how different forms relate to disease activity in JIA. Our aims were to determine allele frequency and plasma concentrations of different Hp forms at higher versus lower JIA disease activity and compare to other APPs.

METHODS

Plasma from JIA (n = 77) and healthy (n = 42) children were analyzed for apparent Hp allelic frequency and densitometric concentrations of alpha forms by Western blot (WB). Polymerase chain reaction (PCR) (buffy coat) was performed in a subset to estimate conformity with genetics. At higher versus lower juvenile arthritis disease activity score (JADAS27) (which includes erythrocyte sedimentation rate (ESR)), total mature Hp concentration from WB was compared and correlated against immunoturbidimetry and total protein, albumin, serum amyloid A (SAA) and C-reactive protein (CRP).

RESULTS

At 300-fold dilution needed to study mature forms in Western blot, precursors were undetectable. Hp2 contributed most signal in most samples. Hp allele frequency was similar in JIA and controls. Both mature forms, taken separately or by sum, declined following treatment, but remained above concentrations of healthy controls, even in a remission subset that achieved JADAS27 < 1. Densitometry correlated with immunoturbidimetry. Hp concentrations correlated with JADAS27, albumin (negatively), CRP and SAA with immunoturbidimetric method correlating strongest to JADAS27 (Spearman R ~ 0.6, p < 0.0001).

CONCLUSION

Hp allele frequency in JIA is similar to the general population, indicating that children with JIA should have the same possibility as in healthy children to produce preHp2 (zonulin), thought to increase intestinal permeability. Circulating Hp concentrations largely parallel other APPs and ESR; none of these measures correlate very strongly to JADAS27 score but Hp can be measured from capillary sampling which is impossible with ESR.

Quantification of Extracorporeal Fibrin Deposits in Haemodialysis with Minimal and Conventional Heparinization

The effects of minimal intermittent heparinization and of conventional heparinization on endogen fibrinogen concentration as well as on fibrin depositis were studied on 17 on patients hemodialysis. It was shown that the minimal intermittent heparinization did non reduce dialysis efficiency and that a total heparin dosage of 6,000 units is the lowest safe limit.

Arterial graft maturation: The duration of thrombotic activity in Dacron aortobifemoral grafts measured by platelet and fibrinogen kinetics

Dacron is thrombogenic, hence small arterial grafts of this material frequently thrombose in the period prior to graft maturation. Anti-thrombotic therapy may therefore be indicated to preserve patency during this risk period. To evaluate the thrombogenicity of immature Dacron grafts, platelet and fibrinogen kinetics using 51Cr and 125I respectively were measured before operation and at 3, 6 and 9 months in 10 patients following aortobifemoral bypass and in 6 age-matched volunteers.

Platelet survival was reduced from 8.8±0.2 d before surgery to 7.4±0.24 d at 3 months. This was accompanied by an increase in platelet turnover from 39±2.4 × 109 l−1 d−1 to 46.9±2.9 × 109 l−1 d−1. Fibrinogen t1/2 fell from 3.72±0.13 d preoperatively to 3.36±0.11 d at 3 months, while fibrinogen fractional catabolic rate rose from 0.27±0.014 to 0.34±0.014. These changes were all significant (P &lt; 0.01). Fibrinogen consumption had returned to normal by 6 months following surgery but platelet kinetics only equated to pre-operative levels at 9 months. We suggest that Dacron grafts are thrombogenically active for about 9 months. When anti-thrombotic therapy is indicated it should be continued throughout this period.

125I fibrinogen turnover in polycythaemia: the effect of phlebotomy

Patients with polycythaemia vera and secondary polycythaemia studied with 125I-labelled fibrinogen, had a significantly increased plasma fibrinogen turnover. The abnormalities were greater in polycythaemia vera and correlated with platelet count but not with packed cell volume. In six patients with polycythaemia vera, phlebotomy reduced the packed cell volume to 0.46 or less. Although fibrinogen turnover decreased significantly in all patients, it remained outside the normal range in four cases. The concept of a prothrombotic state is discussed, and also the importance of these observations with respect to various forms of treatment.

A modified [125I]fibrinogen technique for thrombus detection in the whole leg

The [125I]fibrinogen uptake test was modified to give a quick result, and improve sensitivity and specificity in the diagnosis of deep venous thrombosis (DVT). At least 800 counts were recorded at each measuring point. The leg veins were emptied more effectively. Thus the proximal thigh could be evaluated and the influence of varicose veins reduced. The feet and the leg points were measured in a zig-zag order (from side to side) to avoid systematic errors in early diagnosis. The modified test detected 62% of the thrombi 1 h after injection, 82% after 1 day and 95% after 2 days. The method still lacks in specificity; this is unavoidable since fibrin accumulates in various other conditions than DVT. The combination of high sensitivity and low specificity makes the modified test reliable as a screening procedure, but not as an independent method.

[Autologous 131J-tagged human fibrinogen for early detection of venous thrombosis (preparation, biological and in vivo properties) (author's transl)]

A method for preparation of autologous 131J-tagged human fibrinogen is demonstrated. In vitro the preparation is characterized by content of fibrinogen, protein, plasminogen, clottability and molecular weight. Total plasma radioactivity, specific radioactivity, non-protein-bound radioactivity, biologic half-life and the local activity at the thrombus define the properties in vivo. With the above criteria autologous 131-J-tagged human fibrinogen was shown to be useful for early diagnosis of venous thrombosis.

A rapidly produced 125I labelled autologous fibrinogen: in vitro properties and preliminary metabolic studies in man

The properties of fibrinogen extracted by a precipitation method using glycine at ambient temperatures near neutral pH are described. The simple and reproducible method gives a 73% yield of high purity plasminogen-free fibrinogen in 45 minutes from small volumes of plasma. The protein extract was labelled with 125I using chloramine-T under conditions optimal for fibrinogen stability. The extraction procedure, radio-iodination, desalting, and sterilization take only 70 minutes for completion from the time donor blood is received in the laboratory. The methods, using a specially developed extraction vessel and desalting/sterilizing column, can be used in a small hospital laboratory. Autologous fibrinogen can thus be extracted from patients' blood, eliminating the risk of transmitting hepatitis when it is re-administered. The autologous material, which is 97% clottable and contains less than 0-05% free iodide, is being routinely used as a diagnostic tool in the detection of deep vein thrombosis. The high purity of the preparation facilitates metabolic studies and in vitro experimental work. In vivo results show a mean half-life in three normal volunteers of 3-95 days and a catabolic rate of 25-23% per day with the extravascular space estimated as 24-86%. In 30 surgical patients an expected reduced half-life in plasma was determined with a mean of 3-1 days.