Competing prediction rules for DVT

Safely ruling out deep venous thrombosis in primary care. Ann Intern Med 150 (4):229-35. PMID: 19221374

The history of clinical prediction rules for DVT:

1. The original Wells prediction rule was published in 1995 with 12 predictor variables (PMID: 7752753).
2. Wells modified his rule in 1997 to use only 9 variables (PMID: 9428249).
3. In 2003, Wells revised a 10 point rule that adds a point for history of previous DVT (PMID: 14507948.
4. In 2005, a study in the Annals of Internal Medicine was titled "Wells Rule Does Not Adequately Rule Out Deep Venous Thrombosis in Primary Care Patients." However, this study was started in 2002 and so studied the 1997 version of the Wells rule (PMID: 16027451).
5. Now the authors of the 2005 study have published the performance of their own rule (PMID: 19221374), named the AMUSE rule for "Amsterdam Maastricht Utrecht Study on thromboEmbolism."

We are left with the 2003 Wells rule and the AMUSE rule without a direct comparison. An insightful editorial accompanying the current publication by AMUSE notes that the two rules have similar negative likelihood ratios - actually the Wells rule has a slightly better LR- and has been externally validated.

Regarding the physical examination, both rules include the following findings:

• Distended, non-varicose collateral veins
• Calf circumference discrepancy greater than 3 cm measured 10 cm below the tibial tuberosity

The Wells rule also includes:

• Pitting edema (confined to symptomatic leg)
• Swelling of entire leg
• Localized pain along distribution of deep venous system

In addition to the physical findings, the Wells rule includes the sometimes subjective finding, "Alternative diagnosis at least as likely."

In summary, I appreciate the AMUSE group's efforts at creating a less subjective prediction rule for DVT and look forward to a direct comparison of the current versions of both rules. Until then, I will stay with the Wells rule.

This has been added to http://en.citizendium.org/wiki/Deep_venous_thrombosis.

Citation:

Büller HR, Ten Cate-Hoek AJ, Hoes AW, Joore MA, Moons KG, Oudega R, Prins MH, Stoffers HE, Toll DB, van der Velde EF, van Weert HC, & AMUSE (Amsterdam Maastricht Utrecht Study on thromboEmbolism) Investigators (2009). Safely ruling out deep venous thrombosis in primary care. Annals of internal medicine, 150 (4), 229-35 PMID: 19221374

Postural hypotension in patients with syncope

Arch Intern Med 2009 PMID: 19636031

The authors report that in 2106 consecutive patients 65 years or older admitted for syncope, "Postural blood pressure (BP) recording, performed in only 38% of episodes, had the highest yield with respect to affecting diagnosis (18%-26%) or management (25%-30%) and determining etiology of the syncopal episode (15%-21%)."

• The lower percentages are based on 'strict criteria' for abnormal changes:
  
  
  • drop in systolic BP of at least 20 mm Hg
  • or
  • drop in diastolic BP of at least 10 mm Hg
• The higher percentages are based on 'loose criteria' for abnormal changes:
  
  
  • drop in systolic or diastolic BP of at least 10 mm Hg
  • or
  • systolic BP drop to 90 mm Hg or lower
    
  
  

A systematic review of postural blood pressure measurements has been published by the Rational Clinical Examination (McGee S, Abernethy WB, Simel DL The rational clinical examination. Is this patient hypovolemic? JAMA 1999;281 (11):1022-9. DOI:10.1001/jama.281.11.1022 PMID: 10086438 ) Their meta-analysis concluded that the following changes may occur in normal, euvolemic adults:

• Pulse increase:11 (95CI: 9-13)
  
• Systolic blood pressure drop: 4 (95CI: 2 - 6)
• Diastolic blood pressure drop: 5 (95CI:3 - 8)

Based on the Rational Clinical Examination review, which reveals how difficult it is to interpret orthostatic vital signs and that we cannot simply dichotomize the results into normal and abnormal, I think the strict criteria are better. Even with these criteria, orthostatic vital signs was the most important part of the evaluation for syncope.

This has been added to http://en.citizendium.org/wiki/Syncope and http://wiki.medpedia.com/Clinical:Syncope.

Citation:
Mendu ML, McAvay G, Lampert R, Stoehr J, & Tinetti ME (2009). Yield of diagnostic tests in evaluating syncopal episodes in older patients. Archives of Internal Medicine, 169 (14), 1299-305 PMID: 19636031