PT Classroom - Reliability and Validity for Homan's Sign for the Detection of Deep Vein Thrombosis  ׀ by Chai Rasavong, MPT, MBA

 

Deep vein thrombophlebitis (DVT) is a serious condition that can be asymptomatic and go undetected resulting in death due to a pulmonary embolus. It is a partial or complete occlusion of a vein by a thrombus with a secondary inflammatory reaction in the wall of the vein. An individual is at risk for a thrombus formation if he/she has some degree of venous stasis, has blood that is hypercoagulable, and has experienced an injury to the venous walls (1). Other risk factors for a DVT also include: age greater than 40 years, history of previous DVT or pulmonary embolus, major surgery (particularly of pelvis or lower extremities), obesity, trauma to pelvis or lower extremities, congestive heart failure, prolonged immobilization (particularly spinal core injury), and the use of estrogen replacement therapies or oral contraceptives (1). As physical therapists, it is imperative that we recognize these risk factors in our patients and be aware of a clinical test such as the Homan’s test.

 

To assess Homan’s sign, the patient’s knee is in an extended position and the examiner forcefully dorsiflexes the patient’s ankle (1). A positive sign is indicated when pain in the popliteal region and the calf is elicited as the foot is dorsiflexed. However, some individuals seem to have a different opinion on how this test should be applied (2,3,5). These individuals believe to assess properly Homan’s sign, the patient’s knee must be in a flexed position instead of an extended position. They reason that flexing the knee exerts traction on the posterior tibial vein, which when inflamed, causes the symptom of pain to be elicited. However, they fail to explain the exact mechanism of how this traction on the posterior tibial vein would be increased by flexing the knee. In recognizing the length tension relationship at the knee, one would believe that extension of the knee would result in an increase in traction of the vein instead.

When applying the Homan’s test, a positive sign doesn’t automatically conclude a DVT. In fact, a positive Homan’s sign can be elicited due to factors such as superficial phlebitits, Achilles tendonitis, and injury to the gastroc and plantar muscles (1). Further conditions such as herniated intervertebral discs and shortened heel cords can also result in a false positive (2). A negative Homan’s sign, on the other hand, doesn’t automatically conclude an absence of DVT. Thrombosis that develops in the thigh and pelvic veins are often difficult to detect and patients can often remain asymptomatic (4). Keeping this in mind, it is essential that therapists understand just how reliable and valid Homan’s sign is in detection of DVT.

In a study by McLachlin et al. (4), they compare the premortem clinical findings in the lower extremities of fifteen seriously illed patients with results of postmortem venous dissection of these same patients. They discovered that 12 of the lower extremities contained thrombi and 18 did not. The thrombi that were found were twice as often in the veins of the thigh as in the vein below the knee. Homan’s sign was evaluated on the lower extremities of these fifteen individuals, and the researchers concluded a true positive value of 8% and a flase positive value of 6%. These poor findings for Homan’s test could have been attributed to the infrequency of thrombosis below the knee in this study, and with further interpretation one should also realize that the use of extremely ill patients and a small sample size of postmortem patients could have decreased the power in the statistical interpretation of Homan’s sign.
In another study for the detection of DVT, Cranlet et al. (5) studied 1333 lower extremities (124 individuals) looking at various clinical symptoms including Homan’s sign and comparing it to a phlebogram, a form of x-ray. They found that Homan’s sign obtained a true positive value of 48% and a true negative value of 41%. This was the least reliable of the clinical symptoms for thrombosis that they looked at, which also included muscle pain, tenderness and swelling. It should be taken into consideration, however, that only 104 lower extremities had Homan’s test applied to them, compared to 133 lower extremities assessed for clinical symptoms assessed in the other three categories. This failure to use equal sample sizes could have resulted in a less than favorable outcome in the statistical interpretation of Homan’s sign.

In a similar study using phlebography as evidence of DVT, Haeger (6) also found comparable unpromising findings in looking at clinical symptoms such as positive Homan’s sign for interpreting DVT. He found a true positive value of 33% and a false positive value of 21% for this test. This experiment is again also plagued by an unequal use of sample size in the different clinical symptoms categories, which will again result in a less than favorable outcome in the statistical interpretation of Homan’s sign.

Although these studies were flawed with some threats to design validity, Homan’s sign is still accurately recognized as insensitive, nonspecific and not truly diagnostic for DVT. The literature has shown that it elicits almost as many false positives as it does true positives. Therefore, it can’t solely be relied on to either diagnose or rule out DVT.

Nevertheless, Homan’s test still remains an important tool for use in the health care setting. We, as therapists, realize that this test is easy to perform. Thus, it can be to our advantage to apply Homan’s test in conjunction with other detected clinical symptoms correlated with DVT such as: unexplained fever or tachycardia, muscle pain, tenderness, swelling, temperature change and venous dilation. By doing so, we will be increasing our power and ability to interpret a DVT. This interpretation will than call for a further diagnosis of DVT which can be confirmed by a positive venogram or Doppler flow study with duplex imaging (7).

Besides just focusing on the diagnosis of DVT, a physical therapist should also be aware of the preventive measures for a DVT. Preventive therapeutic measures include: early ambulation (particularly post-operatively), utilization of support stockings or elastic hose, passive or active range of motion, the use of anticoagulation drugs such as heparin, and prevention of any prolonged positions (8). By taking these preventive measures, recognizing the risk factors for development of a DVT, and utilizing Homan’s test in conjunction with other clinical symptoms for DVT, we can greatly decrease the likelihood that our patients will suffer from a DVT that will lead to a pulmonary embolus and death.



References
1) Goodman and Boissonnault. Pathology: Implications for the Physical Therapist. W.B. Saunders Company. 1998;326-329.
2) Shafer N, Duboff S. Physical Signs in the Early Diagnosis of Thrombophlebitis. Angiology. 1971;22:18-30.
3) Dunphy and Bradford. Physical Examination of the Surgical Patient. W.B. Saunders Company. 1953; 162-164.
4) McLachlin J, Richards T, et al. An Evaluation of Clinical Signs in the Diagnosis of Venous Thrombosis. Archives of Surgery. 1962;85:58-64.
5) Cranley J, Canos A, et al. The Diagnosis of Deep Vein Thrombosis. Archives of Surgery. 1976;111:34-36.
6) Haeger K. Problems of Acute Deep Venous Thrombosis. Angiology. 1969;20:219-223.
7) Nunnelee J. Minimize the risk of DVT. RN. 1995;58:28-32.
8) Mathewson M. Homan’s Sign is an Effective Method of Diagnosing Thrombophlebitis in Bedridden Patients: Fact or Myth? Critical Care Nurse. 1983;3:64-65. 6.

 

Last revised: March 8, 2009
by Chai Rasavong, MPT, MBA


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