POTD: HIV Testing in the ED

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Hi everyone,

For my very last POTD, I wanted to talk about a topic requested by our very own Chair, Dr. Eitan Dickman. The question is: what HIV testing is performed in the ED, and how do we do it?

Types of HIV Antibody Testing

1) EIA (Enzyme ImmunoAssay): This is a very common form of HIV antibody testing, and is indeed the testing we do from the MMC ED. ELISA (Enzyme-Linked ImmunoSorbent Assay) testing might be a familiar name to some folks and is a type of EIA. These EIA tests are performed by taking a sample from the patient and combining it with synthetic or native HIV proteins. If there are any HIV antibodies within the patient sample, they will bind with the HIV proteins. Usually a second antibody - an enzyme-linked antibody, hence the name - is then introduced that binds to the HIV antibody to aid in detection. Thus, if the notorious HIV protein/patient HIV antibody/enzyme-linked antibody triplet is detected, then the antibody test is positive. 

However, it is vitally important to keep in mind that this initial EIA antibody test is only a screening test; a positive antibody screening test will automatically reflex to perform a confirmatory test. There are many types of confirmatory tests out there, but the lab advised me that we utilize RNA PCR testing. Which means, at MMC, you need to have a positive HIV antibody screening test + a positive HIV RNA PCR confirmatory test to be diagnosed with HIV. This is important to keep in mind when giving call backs to patients or following up on test results. 

2) Rapid HIV Test: This test can be very useful for point-of-care settings, as the results are available in 20-30 minutes. We do not at the moment have this option, but some other care settings do.

3) Western Blot Test: This was an option for confirmatory testing but has been largely replaced by newer technologies, like our PCR testing.

4) 4th Generation Test: This test is special in that it tests for both HIV antibodies and antigens. By testing for the antigen, called p24, HIV infection can be detected far earlier in the disease course than antibody testing, as antibodies can take up to 12 weeks to develop. This is critical in limiting HIV transmission, as the virus is far more likely to be spread early in the disease course while patients are asymptomatic and/or unaware they are HIV carriers. Our ED testing is not currently an antigen test, but it is good to keep in mind for future practice.

Accuracy in HIV Antibody Testing

The sensitivity and specificity of HIV antibody testing help determine the accuracy of diagnosing HIV in our ED. HIV antibody tests typically have a sensitivity of >99%, meaning very few individuals infected with HIV will be missed by our screening test. However, it is important to keep in mind that the "window period" of time between exposure to HIV and to when the antibody test can detect the infection; given that antibodies, again, can take up to 12 weeks to develop, if a new HIV carrier is tested during this time, there is the possibility of a false negative.

HIV antibody tests also typically have a specificity of >99%, meaning there are very few rates of false positives. Despite this, it is paramount that we also get the confirmatory RNA PCR test in addition to the screening antibody test in order to ensure diagnostic accuracy and limit any anxiety for patients.

Ordering HIV Testing in the ED

Testing for HIV in the ED is incredibly easy. When placing an order, navigate to the "ED Sexual Assault / STI / PID Order Set", click the "HIV-1/2 EIA, SCR W/ RFL", and voila! A specimen of blood, oral fluid, or urine is collected and sent to the lab. If the screening antibody test is positive, again, the confirmatory PCR will automatically be reflexed and sent. Any HIV result is automatically tracked by the ED tele doc, so no need to include it in ED Call Backs. So, really, just ordering it here will do most of the work.

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POTD: Tick Bites

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 Tick Removal – there are multiple tips and tricks to do this, but most sources suggest…

-       Using a pair of tweezers (or forceps) and attempting to grasp the tick as close to the skin surface as possible

-       Pull upwards with gentle, steady traction. Do not jerk or twist

-       Do NOT squeeze, crush, or puncture the body of the tick – this may expel infectious contents

-       After removing the tick, wash skin thoroughly with soap and water

 

What to do if mouth parts remain in the skin?

-       UpToDate says to leave it in and they’ll be expelled on their own

-       WikEM says to excise under local anesthesia… seems aggressive

 

Important Ticks for Identification – The CDC has a good guide. If you’re squeamish with bugs, you’ve been warned and please skip this part. There are 3 main types of ticks found in the US.

 

1)    Ixodes Scapularis or “deer ticks” = LYME DISEASE. Other ticks do not transmit Lyme disease


-       Brown, about the size of a poppy seed but can be larger when engorged

-       Primarily found in the North-East and Midwest, less commonly in the Western US

-       Most famously transmits Lyme Disease, also anaplasmosis, babesiosis

 

2)    Dermacentor species or “dog ticks”

-       Brown with a white collar, about the size of a pencil eraser 

-       Primarily found in the Rocky Mountain States (Colorado, Idaho, Montana, Nevada, Utah, Wyoming, etc.)

-       Most known for transmitting, you guessed it, Rocky Mountain Spotted Fever

3)    Amblyomma Americanum or “Lone Star Tick”

-       Brown or black with a white splotch

-       Primarily found in the South, but can also be found in the Eastern US

-       Most known for Southern Tick-associated rash illness (STARI) and ehrlichiosis

 

Who needs prophylaxis? IDSA recommends prophylaxis only if ALL OF THESE CRITERIA ARE MET. It should be specified that this is for prophylaxis against Lyme Disease only.

-       The tick is identified as a deer tick

-       Tick is estimated to have been attached >36 hours or engorged (it takes time for the bacteria to exit the gut of the tick and enter the bloodstream). Ticks found crawling on skin automatically do not count.

-       The antibiotic can be given within 72 hours of tick removal

-       The bite occurs in a geographic location that Lyme Disease is highly endemic (can be found on CDC website)

-       There is no contraindication to take doxycycline (primarily appears to be hypersensitive or children < 8). If there is a contraindication, no second-line antibiotic exists

 

The prophylaxis is a single dose of 200mg doxycycline, or 4mg/kg up to a max of 200mg for children.

Antibiotic treatment following a tick bite is not recommended as a means to prevent anaplasmosis, babesiosis, ehrlichiosis, Rocky Mountain spotted fever, or other rickettsial diseases. Rather, patients should be warned and be vigilant against symptoms such as fever, rash, or other symptoms concerning for these diseases.

https://www.cdc.gov/ticks/tickbornediseases/tickID.html

https://www.uptodate.com/contents/what-to-do-after-a-tick-bite-to-prevent-lyme-disease-beyond-the-basics

https://wikem.org/wiki/Tick_borne_illnesses

https://wikem.org/wiki/Tick_removal

 

 

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POTD: Rabies Part 2 Rabies Vaccination

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The much anticipated part 2 on rabies. 

Onto the actual important part of this POTD: Rabies post-exposure prophylaxis (PEP). Who gets it and how?

 

Who: UptoDate keeps recommending contacting local health officials for recommendations which, less face it, generally isn’t happening.

-       Anyone with a known or likely exposure to rabies defined as…

o   Bite or saliva-containing scratch from an animal with rabies

o   An open wound or mucus membrane exposure to saliva, CSF, or CNS tissue from an animal with rabies

-       Empirically to anyone with suspected exposure (pretty open-ended) 

-       Exposure of keratinized skin to saliva, blood, feces DOES NOT count as an exposure

 

For domesticated animals

-       High risk: undocumented vaccination status, aggressive behavior

-       If animal (dog, cat, ferret) able to be observed/quarantined for 10 days, can hold off PEP until end of 10-day period

o   Animals almost universally show signs within 10 days of rabies

 

For wild animals

-       High risk: bat, raccoon, skunk, fox

o   Start PEP, discontinue if animal able to be tested promptly and is negative

-       Low risk: squirrel, chipmunk, mouse/rat, rabbit/hare

o   Do not start PEP

 

How: There are 2 components, (1) the rabies vaccine and (2) rabies immune globulin (RIG)

1)    Rabies vaccine – administered 1mL IM specifically in the deltoid region (not gluteus muscle, risk of sciatic damage/lower response to vaccine). Has a very specific dosing schedule

a.     If patient has received pre-exposure prophylaxis: 2 doses, Day 0 and Day 3

b.     If patient unvaccinated: 4 doses, Days 0, 3, 7, and 14

                                               i.     If immunosuppressed, a 5th dose is given on Day 28

c.     Day 0 is first day that rabies vaccine is given

d.     It can be helpful to write the dosing schedule on the discharge papers for future providers (speaking from experience)

2)    RIG – only indicated if patient has not received pre-exposure prophylaxis

a.     20 U/kg – as much as possible infiltrated around the wound with the rest delivered IM in the opposite deltoid of the vaccine arm.

b.     If no obvious wound, place all IM

PEP should be given regardless of delay from time of exposure

Are there any adverse events with vaccination? Depends on the vaccine…

-       Usually local skin reactions (pain, redness, swelling, induration) with possible mild systemic symptoms (fever, headache, GI symptoms)

-       Hypersensitivity or anaphylaxis  can switch to a different vaccine formulation if possible

-       Counseling should be given on these symptoms to prevent patient non-compliance with future doses

  

FAQ

1)    What if they patient doesn’t closely follow the dosing schedule?

 

Small deviations aren’t that important, and doses should be administered at the same intervals. For example, if day 7 dose is actually given on day 10, then the next dose should be scheduled on day 17 (or 7 days later), etc.

 

For more significant delays… consult ID? Seriously though, it likely involves antibody testing and titers, while attempting to follow the initial dosing patient was started on (maybe requires ID follow-up).

 

2)    What if patient received different formulations of rabies vaccine?

 

Just give them what you have and have them follow-up with their PCP or clinic for antibody titers. Theoretically the vaccines are interchangeable but not ideal.

 

3)    What if the patient is pregnant?

 

Not a contraindication, no evidence associated with fetal abnormalities or adverse pregnancy outcomes.

 

4)    If RIG was not initially administered? Like if a traveler returns from a foreign country and needs to have their scheduled doses at specifically YOUR emergency department

 

RIG can be administered on return if less than 7 days from initial vaccine administration. RIG should not be administered afterwards because it interferes with the normal immune response that the vaccine causes.

 

Last, but not least, general wound care like irrigation should always be performed along with tetanus. Antibiotics are a more nuanced discussion, and possibly a POTD for another day (although I lean towards providing a course for patients with animal bites in general).

 

TL; DR – and considerations for a busy, NY ED

-       If there was an exposure (actual bite, found in room with a bat) and patient is concerned – give PEP. No serious adverse events.

-       PEP = vaccines in a specific dosing regimen (0, 3, 7, 14, and maybe 28) and RIG (20U/kg) around the wound and the rest IM

-       Please write the dosing schedule with dates on the discharge papers. This makes this patient encounter incredibly easy for your fast track resident.

 

This is likely more than you ever wished to know about rabies. I learned a lot, like next time Mak needs the rabies vaccine I’ll make sure to give it in his arm instead of his butt.

https://www.uptodate.com/contents/clinical-manifestations-and-diagnosis-of-rabies?topicRef=16595&source=see_link

https://www.uptodate.com/contents/treatment-of-rabies?topicRef=8328&source=see_link

https://www.uptodate.com/contents/when-to-use-rabies-prophylaxis?sectionName=POST-EXPOSURE%20PROPHYLAXIS&topicRef=8303&anchor=H2&source=see_link#H2

https://www.uptodate.com/contents/rabies-immune-globulin-and-vaccine?topicRef=8328&source=see_link

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