Can the docs tell for sure that it's a bite? (Spider or something else)

[Ruken]

Some time ago my sister had what was thought to be a bite from a brown recluse spider or one of its grumpy relatives. She had a nasty rotten necrotic patch on her leg. At some point a doctor took a tissue sample and sent it to a lab, which was able to determine that it was in fact an arthropod bite (as opposed to some sort of bacterial infection.)

My question:

What test did they run and how does it work?

[spingears]

@Ruken

At some point a doctor took a tissue sample and sent it to a lab, which was able to determine that it was in fact an arthropod bite (as opposed to some sort of bacterial infection.)
My question: What test did they run and how does it work?

Possibly a culture and using reagents to react with the sample.
I have a PhD chemist friend who runs a hospital lab. The machine uses a few DROPS of body fluid and runs numerous test. Some sort of micro chemistry system. When done it prints and spits out a complete report. I think he my be overpaid as the machine does all the work. :rolleyes:

[Qadgop_the_Mercotan]

Recently, a passive hemagglutination test was developed for diagnosis of brown recluse envenomation with good sensitivity and specificity that is capable of identifying envenomation up to 2 weeks after the incident. Unfortunately, the test is cumbersome to prepare, and results are not available for 6-24 hours, by which time initiation of a treatment regimen is indicated. Also discouraging use of the passive hemagglutination inhibition test are reports of false-negative results when the specimen contains exudate that is primarily bloody.

http://www.emedicine.com/derm/topic598.htm

So yes there’s a test, but it’s not necessarily that easy to get, or that accurate when it is gotten.

[Qadgop_the_Mercotan]

@Ruken

What test did they run and how does it work?

They might have just done a tissue biopsy too.

One nice thing to know, from the above cite:

Almost all brown recluse spider bites heal nicely in 2-3 months without medical treatment.

[Shagnasty]

Also a link to a current staff report:

http://www.straightdope.com/mailbag/mspiderbite.html

[Ruken]

@Qadgop the Mercotan

So yes there’s a test, but it’s not necessarily that easy to get, or that accurate when it is gotten.

I don’t think that was it. They didn’t test to see if it was brown recluse bite, they just said that it was definately an arthropod bite.

They did do a tissue biopsy. I just don’t know what they did with the tissue to determine that it was an arthropod bite.

This was all a while ago. The wound is healed, alough she has a nice crater in her leg now.

[Qadgop_the_Mercotan]

@Ruken

They did do a tissue biopsy. I just don’t know what they did with the tissue to determine that it was an arthropod bite.

According to my emedicine link above, a tissue biopsy would have shown histologic findings including eosinophils in association with fibrinoid necrosis of the dermal and subcutaneous arteriolar walls, a dense band of neutrophils, panniculitis, occlusive phlebitis, and vascular thrombosis.

I’m not sure what about that sort of finding makes it consistant with an arthropod bite. We’ll have to wait until our SDMB pathologist pops in. Jackmannii?

Glad she’s better.

[Ruken]

@Qadgop the Mercotan

I’m not sure what about that sort of finding makes it consistant with an arthropod bite.

It’s quite possible that someone (myself included) misunderstood or mistated something along the chain of communication from doctor to you all. I asked her if she knew any more details but she said she doesn’t.