Na Na

PRP No test scproph 0/25(0) 0/14(0) bolus iv ther 3/20 (15) 0/10 (0)

No Yes

Note-. HIT was excluded if the platelet count rose during continued heparin after an early fall (e.g., Johnson et al., 1984). Also, where uncertainty existed as to the number of patients with probable HIT, the lower number was indicated in the table, to avoid overestimating the number of patients with HIT (contrast the analysis shown in Table 6). Some data relating to Cipolle et al. (1983) were obtained by personal communication, as reported (Warkentin and Kelton, 1991). The study by Gallus et al. (1980) was excluded because the source of heparin was not specified. Some reports (e.g., Nelson et al., 1978) were excluded because timing of thrombocytopenia was not reported. See Chapter 20 for data in children.

aPowers et al. (1984) described five patients who developed thrombocytopenia during bovine UFH use (none during porcine UFH use); 2 patients whose platelet counts fell beginning on day 7 (to nadir of 41 x 109/L) and on day 8 (to nadir of 53x109/L) had positive testing for HIT antibodies by SRA; test results are not available for 1 patient whose platelet count fell on day 5 (excluded from Table 2, but included in Table 6); 1 patient with proved HIT developed progression of deep venous thrombosis, as indicated in Table 6 (laboratory records of Dr. J. G. Kelton).

bCipolle et al. (1983) described 10 patients who received bovine UFH who may have had HIT; only six are included here, all of whom developed a platelet count fall between days 7 and 10. Ramirez-Lassepas et al. (1984) examined the subgroup with underlying cerebrovascular disease and reported six patients who developed thrombocytopenia after receiving bovine heparin. Only the 3 who developed late thrombocytopenia are reported here.

cOnly eight of 16 thrombocytopenia patients underwent PRP testing (all negative) and only five underwent SRA testing. The 3 who developed late thrombocytopenia (HIT) had negative PRP testing, but did not have SRA testing.

information on timing of platelet count fall to determine the likelihood of HIT was obtained by personal communication, as described (Warkentin and Kelton, 1991). eOrigin of heparin is uncertain and may have used mucosal heparin from sheep; at least 3, and as many as five, patients appeared to have HIT based on in vitro testing and timing of platelet count fall.

'One case of early thrombocytopenia due to DIC reported in original paper was excluded.

9At least four, and as many as nine, patients appeared to have HIT; the four that tested positive for HIT antibodies are included here.

hOne patient appeared to have HIT based on positive heparin rechallenge, despite negative in vitro HIT test. i—

'Thrombocytopenic patients with negative EIA testing were excluded. ro

'Frequencies of HIT in patients with and without previous exposure to UFH or LMWH were 10/598 (1.7%) and 1/1156 (0.3%), respectively. g kThese authors compared the frequency of HIT among a prospective cohort of LMWH-treated neurology patients with their previous UFH-treated patient cohort (p =0.17). Q.

Abbreviations: ATE, arterial thromboembolism; EIA, PF4-heparin enzyme-immunoassay; HD, hemodialysis; HIPA, heparin-induced platelet activation test; HIT, heparin-induced ^

thrombocytopenia; iv ther, intravenous therapeutic-dose heparin; LMWH, low molecular weight heparin; MI/ACS, myocardial infarction/acute coronary syndromes; NA, not applicable; PCI, percutaneous coronary intervention; PRP, HIT assay using citrated platelet-rich plasma (PRP/SR, with serotonin release); sc proph, subcutaneous prophylactic- ®

dose heparin; sc ther, subcutaneous therapeutic-dose heparin; RCT, randomized controlled trial; SRA, serotonin release assay using washed platelets; UFH, unfractionated g.

heparin; VTE, venous thromboembolism.

TABLE 3 The Frequency of HIT: Prospective Studies of Surgical Patients Using Confirmatory In Vitro Laboratory Testing of Patient Serum or Plasma or Indicating a High Likelihood of HIT Based on Timing of Platelet Count Fall

Major --Timing of Definition of indication In vitro Route, Bovine Porcine Fonda- platelet count thrombocytopenia

Study for heparin test dose UFH UFH LMWH parinux fall reported? (x109/L)

RCTs

Leyvraz et al., 1991

Orthopedic

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