Episode 414: 421. Scabies and DUKE criteria

Stavropoulou E, et al. Reassessing the 2023 International Society for Cardiovascular Infectious Diseases Duke clinical criteria for infective endocarditis: Impact of excluding fever and updating diagnostic definitions. Clin Infect Dis 2025 Dec 31; [e-pub]. DOI: 10.1093/cid/ciaf737.

Big takeaways

• About 35% of patients truly had IE.
• Fever showed up in 80% of patients both with and without IE, so it did not help distinguish them.
• Dropping fever from the criteria actually made them better:

• Sensitivity improved: 77% (no-fever) vs 74% (standard).
• Specificity improved a lot: 80% vs 49%.
• "Possible IE" shrank from 39% to 17%, meaning fewer gray-zone cases.
• Only 0.4% of patients without IE were incorrectly labeled as having IE.

Both are widely used and both can work for regular (non-crusted) scabies.

The SCRATCH trial: who won?

In the SCRATCH trial from France, researchers treated about 1000 people in 300 households with confirmed scabies. Each household was randomized to:

Whole-body 5% permethrin cream on days 0 and 10, or

Oral ivermectin (weight-based) on days 0 and 10.

They then checked who was cured at day 28.

Here's what they found:

Household cure rates

Permethrin: 88% cured

Ivermectin: 72% cured

Translation: For every 6 households treated with permethrin instead of ivermectin, one extra household was fully cured (NNT 6).

Index (main) patient cure rates

Permethrin: 92%

Ivermectin: 77%

That's one extra person cured for about every 7 treated with permethrin instead of ivermectin (NNT 7).

Side effect

Skin irritation-type reactions: 14% with permethrin vs 10% with ivermectin.

So permethrin wins on cure, with a small trade-off in local skin reactions.