Table 3
Author, date and countryPatient groupStudy type (level of evidence)OutcomesKey resultsStudy weaknesses
Philbrick JT et al, 1988, USAAll studies of sufficient quality identified from literature search over years 1944 to 1986Literature reviewIncidence PE6 of 163 patients receiving no anticoagulation (Strength of evidence weak). 9 of 208 patients receiving a range of anticoagulation (0 of 32 in only study with strong evidence, all other studies, weak)
Giachino A, 1988, Canada152 patients who died in Ottawa hospitals over a five year period, with PE listed as the cause of death.Retrospective studySource of thrombosis in fatal pulmonary emboli.82 had no postmortem examination. 23 postmortem examinations confirmed PE as the cause of death, and identified the source of the embolus. 3 of 23 postmortem examinations revealed the calf veins as the source of the thrombi.No controlling of postmortem procedures—unclear if all legs veins thoroughly examined.
Only 23 of 152 considered to die from PE actually had a PM and had the source of the embolus confirmed.
Lohr J et al, 1991, USA75 patients with ultrasound diagnosed calf thrombosis. Treatment left to physician’s discretion.Prospective study with follow up serial ultrasound examination.Thrombosis propagation15% propagated to involve the popliteal or larger veins. A further 17% propagated within the calf veinsPublication bias—all of these patients may have been included in the study by Pelligrini V et al, 1993.
No information regarding the length of follow up, or the effect of varying therapies
Pellegrini V et al, 1993, USA25 patient with isolated calf DVT and 12 patients with superficial or muscular calf thrombosis, diagnosed by venography on postoperative screening of total hip arthroplasty patients. Only 12 calf DVTs and one superficial/muscular calf thrombosis were anticoagulatedProspective study following up at 6, 12, 24 and 52 weeksIncidence of PE4 of 13 untreated calf DVT patients were diagnosed with PE. 0 of 1 treated calf DVT patient and none of the superficial/muscular calf thrombosis developed PETwo of the PEs were diagnosed on the strength of sudden collapse and cardiac arrest—no postmortem examination carried out
Nielson HK et al, 1994, Denmark15 patients with venographically diagnosed calf DVTs.Prospective studyVQ scan result at presentation5 of 15 had positive VQ scansNo information regarding exact criteria for diagnosing PE from VQ scan alone—probable over-estimation of incidence
VQ scans were performed at 10 and 60 days, however no information regarding the breakdown of subsequent PEs between proximal and isolated calf DVT groups
Lohr JM et al, 1995, USA192 patients with ultrasound diagnosed below knee DVTs, Treatment left to physicians discretionProspective study with serial ultrasound for four weeksThrombus propagation53 of 139 thrombi propagatedPublishing bias—the cohort appears to include all of the patients included in the previous Lohr study (see study in this table)
Paper does not establish rate of PE
O’Shaughnessy AM et al, 1997, Ireland50 patients with ultrasound diagnosed DVTs, 43 treated with anticoagulation and 7 withoutProspective study, using repeat ultrasound at one week, one month, six months and one year.“Outcome” of isolated calf thrombosis.3 patients presented initially with a “positive” VQ scan. One fatal PE within the first month.Venography not used to diagnose initial calf DVT. Apparently, no attempts were made to actively seek the diagnosis of PE throughout the follow up period. No adequate description of the positive VQ scans. 10 patients lost to follow up at six months. No account taken of the effect of treatment
Gottlieb RH et al, 1999, USA238 patients with ultrasound diagnosed below knee DVTsRetrospective studyIncidence of diagnosed PEs2 of 56 patients not receiving anticoagulant therapy had PEPatients were not identified using venography. Retrospective study, therefore unable to detect silent PEs or those that did not present to medical services. One PE diagnosed on strength of high probability VQ scan alone. No description of frequency of follow up ultrasound scans. Therapy at the discretion of physician. No information regarding anticoagulant therapy for patient with extension to thigh DVT. 28 patients were not followed up for the full six months as they died
Incidence of extension into thigh DVT1of 227 receiving anticoagulant therapy had documented extension to thigh DVT
Pinede L et al, 2001, France105 patients with calf DVTs treated for six weeks with warfarin, 92 patients with calf DVTs treated for 12 weeks with warfarinProspective studyIncidence of PE1 of 197 (patient from 12 week warfarin group) had documented PEDiagnosis did not always use venography
No information regarding which symptoms would prompt investigations for PE. Method’s description implies that a VQ scan result of intermediate probability would diagnose PE—no information as to how this PE was diagnosed
Schwarz T et al, 2001, Germany84 patients with isolated calf muscle thrombosis. 52 received LMWH for 10 days, 32 received no anticoagulationProspective cohort with serial ultrasound examinationsProgression to deep veins of calfStudy discontinued as 8 of 32 non-anticoagulated patients progressed to deep veins thrombosis, compared with 0 of 52 anticoagulated patientsGold standard venography not used
VQ scan results interpreted in isolation
Sharpe RP et al, 2002, USA85 trauma patients with below knee DVTsProspective cohortThrombus propagation4 of 85 thrombi propagated proximallyGold standard investigations not applied for DVT or PE
PE1 of 85 did not propagate but had a PE