NMS Q&A Family Medicine

Peripheral Vascular Disease 51Examination Answers1. The answer is E. MRI is the best choice among the fiveoptions given for diagnosing osteomyelitis. The CT scanis less sensitive and literally carries infinitely more radiationthan the MRI (MRI has no radiation and the CT scanconveys approximately 200 times the radiation of a chestx-ray. Plain x-ray is inadequately sensitive, and the othertwo choices are significantly less sensitive.2. The answer is D. D-dimer among the listed non-invasivetests would be most sensitive for venous thrombosis.D-dimer is 95% to 97% sensitive and confers a very highpositive predictive value. A value greater than 500 ng/mL isthe cut-point above which sensitivity is significant. Veryclose to this sensitivity is that found with compressionvenous ultrasound that is 94% sensitive and also confers ahigh positive predictive value. Bone scan has no applicabilityin vascular disease; plain x-rays, of course, have low sensitivityfor soft tissue diseases. The time-honored Homan’ssign, deep calf pain caused by manual squeezing of the calf,is only 50% sensitive and is associated with many false positives,for example, myositis and local infection.3. The answer is C. The Well’s criteria comprise a pointsystem to assist in evaluating for PE. The following is atabulation of that system:Modified Well’s criteria for PE:Symptoms of DVT 3.0Other Diagnosis less likely 3.0Heart rate 100 1.5Immobilization or surgery ( 4 weeks) 1.5Previous DVT or PE 1.5Hemoptysis 1.0Malignancy 1.0A score of 6 points signifies a highprobability of PE2–6 points signifies a moderate probability of PE 2 points indicates a low probability of PEThe gold standard for diagnosis of PE is angiography. TheVQ scan has high sensitivity but low specificity—that is,high negative predictive value.4. The answer is D. Although DVT lies within the differentialdiagnosis of this case, the vignette places thepatient in the 0% to 13% probability by the Wells clinicaldecision rules (CDRs) for assistance in diagnosing DVT.The Wells CDRs, with a maximum point of 9, show thispatient to have 2 points. After 2 points are subtracted forthe possibility of another diagnosis (cellulitis) that couldaccount for the findings, the net score is 1. This confers a0% to 13% possibility of DVT (see Table 7–1 ). Therefore,the patient may be followed expectantly while he istreated symptomatically or empirically. This patient maywell have a case of cellulitis secondary to an infection ofthe great toe, for which culture, white blood cell countand differential, empiric prescription of antibiotics, andwarm compresses would be appropriate. Another strongfactor in a case like this, ignored in the Wells criteria, isthe normal D-dimer. The latter is sensitive for the presenceof intravascular thrombosis, though insignificantlyspecific.5. The answer is A. According to the Wells CDR scale,this patient has a score of 4, placing her in the highprobabilitycategory for DVT (Table 7–1). Even in the faceof negative ultrasonographic studies, a venogram shouldbe ordered, although if the Wells score were in the moderatecategory, then serial ultrasonography would be acceptable.Prescribing cefadroxil (Duricef) would be a goodchoice for infection below the waist, but there is no evidencefor infection in the vignette. Surgical exploration isinappropriate, and checking for metastatic disease has asecondary priority at this point.TABLE 7–1 Wells CDRClinical CharacteristicScoreActive cancer (within 6 months) 1Paralysis, paresis, or recent plaster immobilization 1of lower extremitiesRecently bedridden for more than 3 days or1had surgery within 12 weeksLocalized tenderness along the distribution1of deep veinsEntire leg swollen 1Calf swelling to 3 cm more expected for1symptomatic sidePitting edema confined to the symptomatic leg 1Collateral superficial veins 1Previously documented DVT 1Alternative diagnosis at least as likely as DVT 2Source : Modified from Smucny J , Cohania R . American Family Physician( 2004 ; 70 : 565 ).Notes : To determine the probability of DVT, calculate the score andplace the patient in one of the following categories: 0 lowprobability (0% to 13%); 1 to 2 moderate probability (13% to30%); 3 high probability (49% to 81%).