This question came up when one of my co-residents stated during our discussion of a case that the patient, who had HIV, should not be considered immunosuppressed because his CD4 count was in the 300s.
Patients who are HIV-positive with a CD4 count <200-250 or who have had an AIDS-defining illness are immunocompromised. Patients with a CD4 count above this level may not necessarily count as immunocompromised.
As a reminder, CD4 counts dictate what patients should be prophylaxed against:
CD4 <250: IgG and IgM serologic screening for coccidiomycosis in endemic regions, administer fluconazole if positive.
CD4 <200: administer Bactrim/dapsone/atovaquone for PJP prophylaxis
CD4 <100: administer Bactrim or alternative for toxoplasmosis prevention. Patients are at risk for cryptococcus.
CD4 <50: patients are at risk for MAC, and if not on antiretrovirals, should be prophylaxed with azithromycin (if on ART, do not need prophylaxis)
A list of AIDS-defining illnesses from the CDC (see website for more details on the asterisks/caveats):
Bacterial infections, multiple or recurrent*
Candidiasis of bronchi, trachea, or lungs
Candidiasis of esophagus†
Cervical cancer, invasive§
Coccidioidomycosis, disseminated or extrapulmonary
All too frequently, patients are started on antibiotics for a UTI because of a “positive UA” alone. This should not be! Sometimes, especially if a patient is unstable or really sick, it may be wise to empirically treat for a UTI, but in an otherwise stable patient, please think carefully about whether they truly have a UTI.
Technically, a UTI is defined in part by a positive urine culture that has >10,000 organisms, of no more than two species. (“Mixed genital flora” does not count!) However, often we let this slide if a patient has a “positive UA” and one of the following criteria:
fever >38.0 C
suprapubic tenderness or CVA tenderness
If a patient has a Foley in place, they will not be able to reliably tell you about urgency, dysuria, or frequency because the Foley catheter itself can cause these symptoms.
You may see Candida growing because of a chronic in-dwelling urinary catheter, instrumentation/urologic procedures, contamination, or because of a true UTI or even bloodstream infection.
If the patient has a catheter, remove it and see if the Candida persists. If it cannot be removed, replace it with a new one.
Asymptomatic candiduria should only be treated in high-risk populations: neutropenic patients and those undergoing surgery or urinary tract procedures. Also, if the patient has dysuria, then it should be treated. Most strains are susceptible to fluconazole so this is a first-line agent.
“If your patient has a negative MRSA nasal swab, and you are using vancomycin to empirically cover hospital-associated pneumonia, you can stop the vanc.”
Yes!!! It turns out this is true. There was a study in 2014 from Arizona that looked at how MRSA nasal swab results correlated with MRSA pneumonia: “The MRSA PCR assay demonstrated 88.0% sensitivity and 90.1% specificity, with a positive predictive value of 35.4% and a negative predictive value of 99.2%.” This means that although a positive MRSA swab doesn’t mean your patient will get MRSA pneumonia, if they are negative for MRSA, there is an excellent chance that they will not have MRSA pneumonia and so empiric vancomycin is not indicated unless there are extenuating circumstances. This was also seen in an earlier study.
Interesting aside: another study looking at rates of MRSA disease found that patients can still develop MRSA infections even if their nasal swab is negative though: “nearly a third of MRSA-infected patients were not nasally colonized, suggesting that nasal colonization need not precede disease and that a negative test for nasal colonization would not rule out MRSA disease in settings of moderate or high prevalence.”
Although there is a pretty standardized regimen for someone with HSV encephalitis–10 mg/kg per dose every eight hours for 14-21 days– the regimen for HSV meningitis is less clear. Specifically, one question: when can you switch over from IV acyclovir to PO valacyclovir (Valtrex)?
PO valacyclovir, although converted through first-pass metabolism into acyclovir, is less able to penetrate the CNS than IV acyclovir. There are no clear guidelines, but a good rule of thumb is that someone with HSV meningitis should receive at least 7 days of IV acyclovir before being evaluated for a PO regimen of valacyclovir or acyclovir.
NB: HSV PCR is the diagnostic test of choice for HSV encephalitis or meningitis. However it may lose its sensitivity after the first week of infection. PCR > viral culture in terms of sensitivity and specificity.
The first step, even before starting treatment, is to identify who would be at risk for fungemia. Risk factors include neutropenia, being in the ICU, on TPN, on broad spectrum antibiotics, long-time central-line. Fungus in the sputum or urine may be a red herring, but fungus in the blood is NEVER normal.
Treating fungus depends on what kind it is. The major strains include:
C. krusei (which is virtually fluconazole-resistant)
If a patient without risk factors at an institution where <15% are fluconazole resistant, it’s safe to treat with fluconazole. However, if not, then micafungin or even the terrible amphotericin B may be used.
P.S.- patients with fungemia should get a formal ophthalmology consult!
When do you get a vanc trough? What about a peak? What does it mean, anyway?
Vancomycin is a renally cleared drug used to treat serious infections. A vanc TROUGH is obtained when you expect the patient to be treated for a serious/life-threatening infection, to be treated with other nephrotoxic medications at the same time, or to be treated for >4 days. A trough should be obtained within 30 mins before the 4th dose.
A vanc PEAK is obtained less frequently, when high penetration of a hard-to-reach space is required (osteomyelitis or endocarditis). It should be obtained an hour after vanc finishes infusing.
A RANDOM vanc level should only be obtained in patients on dialysis or with severe renal disease.