UK standard of care and some other useful tests Matthew Williams UK CAB Tests and monitoring in HIV infection UK standard of care and some other useful tests Tests and monitoring in HIV infection CD4 count Viral load Resistance Therapeutic drug monitoring
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After infection, viral load surges to a very high for the first weeks or months
Often 1,000,000+ copies in a millilitre (mL) of blood, when you are very infectious
Viral load falls as the body controls HIV infection then rises over time as immunity is damagedTests and monitoring in HIV infection
Minority species of resistant virus may be missed by conventional resistance testing (ie if less than 10% of your virus is resistant the test may not pick this up).
In patients without evidence of transmitted resistance, a suboptimal virological response to first-line therapy (<1 log10 copies/mL drop in viral load by 4–8 weeks) should prompt resistance testing at that time.
BHIVA, Treatment of HIV-infected adults with antiretroviral therapy (2006)Tests and monitoring in HIV infection
Drug levels vary – much evidence of this – recommended dose is based on averages
University of Liverpool TDM audit – 20-25% of children on NNRTIs or PIs using drugs below therapeutic level.
http://www.i-base.info/htb/v7/htb7-6/University.htmlTests and monitoring in HIV infection
BHIVA – TDM for management of drug interactions, pregnancy and paediatrics, highly treatment-experienced patients when TDM and resistance test results can be integrated, kidney or liver impairment, transplant patients, drug toxicity, alternative dosing where safety and efficacy has not been establishedTests and monitoring in HIV infection
Serum creatinine (blood, not very specific or sensitive)
Creatinine clearance (blood and/or urine samples over 24 hours)
Calculated creatinine clearance (1 blood sample) – also called estimated glomular filtration rate (eGFR)
Creatinine clearance can increase in pregnancyTests and monitoring in HIV infection
AST, ALT, ALP, GGT and bilirubin
Many conditions, some specific indications, complicated by hepatitis B and C coinfection, pharmacological agents (all kinds) and food
Drugs: ritonavir, nevirapine, efavirenz, tipranavir, atazanavir, indinavir, d4T - most ARVS and many other drugs may affect the liverTests and monitoring in HIV infection
Hepatitis C coinfection – liver and diagnosis
http://www.i-base.info/guides/hepc/hcvtesting.htmlTests and monitoring in HIV infection
Red blood count (RBC) 3.8 to 5 W 4.5-6.5 M million per mm3
White blood count (WBC) 4-11 per mm3
Haemoglobin (HGB, Hg) 11.5-16.5 W 13-18 M g per 100mL
Neutropils 2-7.5 per mm3
Lymphocytes 1.3-4 per mm3
Platelets 150-440 per per mm3
Mean corpuscular volume (MCV) 80-97Tests and monitoring in HIV infection
Biggest causes of odd results are ‘sampling error’, ‘processing error’ or ‘sample contamination’
wrong tube, wrong person's sample, cross-contamination, sample too hot/cold/old, wrong reagent, wrongly set up equipment, not reading instructions, misreading output...Tests and monitoring in HIV infection