Low-molecular-weight heparin versus standard heparin in general and orthopaedic surgery: a meta-analysis

Low-molecular-weight heparins (LMWHs) have theoretical advantages over standard heparin as postoperative thromboprophylactic agents. We conducted a meta-analysis of studies reported between 1984 and April, 1991, in which LMWHs were compared with standard heparin for postoperative prophylaxis. We included only randomised studies (reported in English, French, or German) in which investigators compared currently recommended doses of the agents and used adequate screening techniques for deep vein thrombosis. For all surgical studies the relative risk (LMWH versus standard heparin) for deep vein thrombosis was 0.74 (95% Cl 0.65-0.86), for pulmonary embolism 0.43 (95% Cl 0.26-0.72), and for major bleeding 0.98 (95% Cl 0.69-1.40). Comparable relative risks were observed for the general and orthopaedic surgery studies separately. When the analysis for the general surgery studies was limited to those of strong methodology, assessed by eight criteria defined in advance, the benefit/risk ratio was less favourable--relative risk for deep vein thrombosis 0.91 (95% Cl 0.68-1.23), for major bleeding 1.32 (95% Cl 0.69-2.56). There is at present no convincing evidence that in general surgery patients LMWHs, compared with standard heparin, generate a clinically important improvement in the benefit to risk ratio. However, LMWHs may be preferable for orthopaedic surgery patients, in view of the larger absolute risk reduction for venous thrombosis.

Subcutaneous heparin compared with continuous intravenous heparin administration in the initial treatment of deep vein thrombosis. A meta-analysis

OBJECTIVE

To quantitatively assess the efficacy and safety of published randomized trials comparing subcutaneous heparin with continuous intravenous heparin for the initial treatment of deep vein thrombosis.

DATA IDENTIFICATION

Studies published between January 1986 and April 1991 were identified through computer searches of the MEDLINE database and through reviews of the Science Citation Index, Current Contents, proceedings and abstract books, and references cited in the identified articles. Complete manuscripts were obtained from the authors if only abstracts were available.

STUDY SELECTION

Eight clinical trials were identified that compared subcutaneous with intravenous heparin administration in patients with venographically confirmed deep vein thrombosis.

DATA EXTRACTION

Each study was independently analyzed for the percentage distribution of thrombosis, the method of outcome measurement, and the heparin dose. The methodologic strength of each study was assessed using predefined standards for the proper evaluation of a therapeutic intervention with particular emphasis on the type of patient allocation and objective measurements.

RESULTS OF DATA ANALYSIS

The overall relative risk for efficacy (defined as prevention of extension and recurrence of venous thromboembolism) of subcutaneous compared with intravenous heparin treatment was 0.62 (95% CI, 0.39 to 0.98), whereas for safety (defined as major hemorrhage) it was 0.79 (CI, 0.42 to 1.48).

CONCLUSIONS

The results of our meta-analysis indicated that heparin administered subcutaneously twice daily in the initial treatment of deep vein thrombosis is more effective and at least as safe as continuous intravenous heparin administration. Administration of heparin subcutaneously may simplify patient treatment and could facilitate home treatment.

Mortality in hereditary antithrombin-III deficiency--1830 to 1989

To determine whether antithrombin-III (AT-III) deficiency leads to an excess mortality, we studied 171 individuals from ten families with a proven hereditary deficiency. 73 were classified as certainly deficient either by direct measurement of AT-III concentration or by mendelian inheritance patterns. 98 individuals had a high probability (0.5) of deficiency. The 64 deaths recorded did not exceed those expected for the general population adjusted for age, sex, and calendar period. We suggest that a policy of prophylactic anticoagulation for patients with AT-III deficiency cannot be recommended.

[Can nearly finished medical students interpret their professional literature?]

The ability of senior medical students to interpret clinical research articles was examined by means of a written examination based upon two papers from general medical journals. The subjects of the articles were a diagnostic test and a therapeutic trial respectively. Knowledge of basic methodological and statistical concepts mentioned in the articles was in 86% of the students examined (n = 90) below the minimal level required for correct interpretation. 60% of the participants could not correctly apply the results mentioned in the diagnostic paper to a written clinical problem, and 11% could not apply the result of the therapeutic trial. From the reasons the participants gave for their decisions it appeared that 77% and 35% respectively had not been able to interpret the articles correctly. A comparison between self-rated knowledge and results of the test showed that the students tended to overestimate their knowledge. Knowledge of basic concepts of clinical epidemiology and statistics of these nearly graduated medical doctors is insufficient, and many of them cannot interpret clinical research articles correctly.