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Three Part Question

Is [injecting drug use] a [risk factor] for [deep vein thrombosis]?

Clinical Scenario

A thirty year old man presents to the department with a swollen leg, admitting to a recent history of injecting drug use. You suspect he has a deep vein thrombosis but injecting drug use does not feature as a risk factor on the Wells criteria- the widely used model for assessing pre-test probability for this condition, and you wonder if this reflects the incidence rate for deep vein thrombosis in this patient group.

Search Strategy

Ovid Interface
MEDLINE 1966 - January Week 4 2006
[exp Substance abuse, intravenous OR intravenous drug use$.mp OR exp Substance-Related disorders OR exp Injections, intravenous OR drug abuse.mp OR exp Heroin Dependence OR exp Heroin OR heroin.mp OR illicit drug$.mp OR exp street drugs OR injecting drug use$.mp OR drug depend$.mp OR drug addiction.mp] AND [exp venous thrombosis OR deep vein thromb$.mp OR DVT.mp] AND [risk factor$.mp OR exp Risk Factors OR clinical risk.mp OR probability.mp OR exp Probability OR prevalence.mp. or exp Prevalence/] LIMIT humans and english language.

Search Outcome

66 papers were identified of which 11 were shortlisted for their relevance to the question. 5 papers displaying best evidence are shown in the table below.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Syed FF and Beeching NJ. Feb 2005 UK	232 patient episodes of lower limb DVT.	Retrospective case-note review.	To obtain a profile of DVT patients in routing clinical care and determining the contribution of injecting drug use.	Injecting drug use accounted for 6.9% of all episodes and 48.4% of episodes in patients aged < or =40 yrs.	Retrospective. Objective testing for clinical diagnosis are not clearly defined. Seven patients were diagnosed and included in the study without a definitive diagnosis, but from clinical findings alone.
Lui HS et al. Dec 2002 Hong Kong.	376 Hong Kong Chinese patients with objectively diagnosed venous thromboembolism.	Retrospective study.	To estimate the incidence and characteristics of venous thromboembolism in the Hong Kong Chinese population.	The annual incidence of venous thromboembolism in the Hong Kong Chinese population is estimated at 16.6 events per 100 000 population. Injecting drug use is one of the 4 most commonly associated risk factors for diagnosis of DVT with 50/376 (13.3%) cases (49 DVT and 1 PE), particularly in patients <45 years old.	Retrospective.
Shultz S et al. Feb 2002. Berlin.	Injecting drug users admitted into hospital (over the course of a 6yr period) and examined by ultrasound, with symptoms or clinical findings in the inguinal region, with computed tomography used as a reference standard test if an abscess was suspected.	? prospective or retrospective cohort.	To examine the value of colour duplex ultrasonography for the clinical evaluation of injecting drug users with damage to the groin vessels.	77 patients were examined. The most frequent finding was venous thrombosis which was diagnosed in all patients (100%: 63 had complete occlusion of the femoral vein and 14 had non-occlusive/partial thromboses). All patients had various additional co-morbid complications. CT had little effect on therapeutic decisions.	Appears retrospective.
McColl MD et al. Mar 2001. Scotland, UK.	322 consecutive women aged 16-70 years with objectively confirmed symptomatic venous thromboembolism.	Prospective cohort study.	To determine precipitating factors for thrombosis.	187 diagnoses of DVT; 116 with definitive (or possible) PE; 19 had both DVT and PE. injecting drug use was a common risk factor accounting for 21.4% of all cases of DVT, and 52.4% of cases in those aged < 40yrs.	A number of women injecting drug users with a 'clinical' diagnosis of DVT were also known to the researchers but not included in the paper as they lacked a definitive diagnosis; however, inclusion of these patients suggest injecting drug use is the most common risk factor for DVT in Glaswegian women.
Williams PG et al. Jul 1997. South Africa.	86 patients; 121 episodes of patients presenting with complications associated with self-injection of Wellconal.	Retrospective analysis.	Complications of Wellconal abuse.	Opiate overdose was the most frequent diagnosis (32%) followed by endocarditis (20%) and then DVT (12%).	Retrospective.
Lisse JR et al. Oct 1989. Texas, US.	12 cases of upper-extremity DVT; 35 cases of lower-extremity DVT.	Retrospective study.	Con-committent illnesses; presence of intravenous drug abuse.	5/12 (42%) of UEDVT; 4/35 (11.4%) of LEDVT, were cases associated with intravenous cocaine abuse. Interestingly, the authors state that none of the cases of LEDVT had a history of injecting into their groin.	Diagnosis was made in some of the patients with plethysmography which is less specific than more recent modes of diagnostic technique.

Comment(s)

Recognition of injecting drug use as an independent risk factor for deep vein thrombosis is not widely recognised in the literature in this field, though is often referred to anecdotely (Baldeweg), and as a result is not accounted for in our clinical practise. In particular, the widely used Wells criteria for pre-test probability of DVT fails to recognise the significance of injecting drug use as a variable for predicting this disease. Recognition of its importance as a major risk factor may in turn affect our diagnostic management of this patient group.

Clinical Bottom Line

Though literature is scarce, injecting drug is an independent risk factor in the diagnosis of acute deep vein thrombosis and patients with this complication should be managed accordingly.

References

1. Syed FF and Beeching NJ. Lower-limb deep vein thrombosis in a general hospital: risk factors, outcomes and the contribution of intravenous drug use. QJM 2005;98(2):139-45.
2. Liu HS, Kho BC, Chan JC, Cheung FM, Lau KY, Wu WC and yau TK. Venous thromboembolism in the chinese population-experience in a rgional hospital in Hong Kong. Hong Kong Medical Journal. 2002;8(6):392-93.
3. Shultz S, Beckenbach C, Phillipp M and Hengstmann J. Color xoded duplex sonography of inguinal vessels in i.v. drug addicts. Vasa. 2002;31(1):7-13.
4. McColl MD, Tait RC, Greer IA and Walker ID. Injecting drug use is a risk factor for deep vein thrombosis in women in Glasgow. British Journal of Haematology. 2001;112(3):641-3.
5. Williams PG, Ansell SM and Milne FJ. Illicit intravenous drug use in Johannesburg- medical complications and prevalence of HIV infection. South African Medical Journal. 1997;87(7):889-91.
6. Lisse JR, Davis CP and Thurmond-Anderle ME. Upper extremity deep vein thrombosis: increased prevalence due to cocaine abuse. American Journal of Medicine. 1989;87(4):457-8.
7. Baldeweg SE. Injecting drug use is a major risk factor for deep vein thrombosis. BMJ 2000;321:1018.