tests and monitoring in hiv infection uk standard of care and some other useful tests matthew...
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Tests and monitoring in HIV infection
UK standard of care and some other useful tests
Matthew WilliamsUK CAB
Tests and monitoring in HIV infection
CD4 count
●Blood test●Used to judge how far HIV disease has advanced●Helps predict the risk of opportunistic infections●Most useful when it is compared with the count obtained from an earlier test.
Tests and monitoring in HIV infection
CD4 count
CD4 dips on HIV infection from a normal count of 500-1,500 cells in a cubic millimeter (mm3) of blood (a drop, more or less), recovers somewhat, then falls over time down to as low as 0.
Tests and monitoring in HIV infection
CD4 count
CD4 <200 = greater risk of opportunistic infections (OIs) = “AIDS” = threshold for prophylaxis eg for PCP = bottom of UK threshold for starting combination therapy
CD4 <50 = very great risk of OIs
Tests and monitoring in HIV infection
CD4 count
CD4 over 350: treatment not recommended
CD4 any count: treatment recommended if “symptomatic”
BHIVA, Treatment of HIV-infected adults with antiretroviral therapy (2006)
Tests and monitoring in HIV infection
CD4 count
CD4 count lower in pregnancy – temporary drop of 50 cells/mm3
Tests and monitoring in HIV infection
CD4 count
CD4% - CD4 cells as proportion of all lymphocytes (white blood cells), normally about 40% in adults
CD4% is used to monitor babies and children who have higher CD4 counts
Tests and monitoring in HIV infection
Viral load
●Blood test (can be other serum eg CSF)●Used to judge whether treatment is working (early infection?)●Helps predict the risk of disease progression?●Most useful when it is compared with the count obtained from an earlier test.
Tests and monitoring in HIV infection
Viral load
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 damaged
Tests and monitoring in HIV infection
Viral load
When you are on HIV treatment, your viral load should be reduced to “undetectable” = <50 copies/mL = 1.7 log
10
Tests and monitoring in HIV infection
Viral load
Blip = 1 viral load test detectable (over 50 copies) – 2 of these may be a trend and indicate “virological failure”
Tests and monitoring in HIV infection
Viral load
Viral load is usually a PCR (polymerase chain reaction) quantitative (counting) test for HIV RNA - research tests can measure viral load below 50 copies
Other tests: bDNA (branched DNA), NASBA (nucleic acid sequence based amplification)
Tests and monitoring in HIV infection
Resistance test
●Blood test (can be other serum eg CSF)●Used to judge whether treatment will work●Involves interpretation●Two types: genotype and phenotype●Viral load needs to be over 500 copies/mL for the test to work
Tests and monitoring in HIV infection
Resistance test
Genotype looks at genetic make up of HIV viruses in infection and compares this to what is known about which mutations lead to resistance
Phenotype looks at whether the drugs work in a test tube
Tests and monitoring in HIV infection
Resistance test
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
Therapeutic drug monitoring (TDM)
Measures drug levels in the blood - requires blood samples at recorded time intervals after a drug dose
Practical uses for NNRTIs and PIs
Tests and monitoring in HIV infection
Therapeutic drug monitoring (TDM)
Freely available at low (£45/drug) or no cost (if covered by drug company) from University of Liverpool Department of Pharmacology.
http://www.hiv-druginteractions.org/
http://www.delphicdiagnostics.com/
Tests and monitoring in HIV infection
Therapeutic drug monitoring (TDM)
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.html
Tests and monitoring in HIV infection
UK standard of care (BHIVA)
All patients should have:i) a resistance test at diagnosis, ii) before starting HAART, iii) if viral load does not drop by <1log
10 after 4-
8 weeks after starting HAART, (genotype) iv) after virological failure
Tests and monitoring in HIV infection
UK standard of care
BHIVA – viral load before and 4-8 weeks after starting treatment (as necessary
thereafter)
Tests and monitoring in HIV infection
UK standard of care
BHIVA – CD4 count before treatment (as necessary thereafter)
Tests and monitoring in HIV infection
UK standard of care
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 established
Tests and monitoring in HIV infection
● Liver enzymes● Kidney function● Urine● Albumin● Bone density● Glucose● Platelets● Red blood count● White blood count● Lipids
Tests and monitoring in HIV infection
● C-reactive protein● DEXA scan● Chest x-ray● Sputum serology● Lactic acid and blood pH● Haemoglobin and iron● Serum urea● Creatine phosphokinase and lactate
dehydrogenase● Electrolytes
Tests and monitoring in HIV infection
Tests = blood, blood and more blood...
Many tests require a blood sample
Tests and monitoring in HIV infection
Blood glucoseBlood cholesterols and triglycerides
Kidney functionC-reactive protein
Liver enzymes
AnaemiaLactic acidosis
Tests and monitoring in HIV infection
Blood glucose
Normal range 4-8 millimoles per litre (µmol/L)
High glucose ?= kidney disease, neuropathy, insulin resistance, cardiovascular disease
Drugs: PIs, tenofovir, AZT?
Tests and monitoring in HIV infection
Blood cholesterols and triglycerides
Low-density lipoproteins (LDLs) or "bad" cholesterol, and high-density lipoproteins (HDLs) or "good" cholesterol – ratio is key measure
Insulin resistance, metabolic syndrome, cardiovascular disease
Drugs: PIs, AZT, efavirenz
Tests and monitoring in HIV infection
Blood cholesterols and triglycerides
Total cholesterol
Target level under 5.2 µmol/L (4-6.4 µmol/L)
Tests and monitoring in HIV infection
Blood cholesterols and triglycerides
LDL cholesterol
Target level under 3.4 µmol/L
Tests and monitoring in HIV infection
Blood cholesterols and triglycerides
HDL cholesterol
Target level over 0.9 µmol/L
Tests and monitoring in HIV infection
Blood cholesterols and triglycerides
Cholesterol – CV risk cannot be judged on cholesterol levels alone, HDL:LDL ratio, lifestyle, BMI, age and other factors are important
Smoking!
Tests and monitoring in HIV infection
Blood cholesterols and triglycerides
Triglycerides
Fasted levels <2.2 µmol/L normal, 2.2–4.4 µmol/l borderline, >11 µmol/L very high
Each +1.1 µmol/L increased the risk of a heart attack by about 25% in men and 60% in women
Tests and monitoring in HIV infection
Urine
Dipstick test
●Protein – kidney (tenofovir) << mostly albumin●Glucose – insulin resistance (PIs), kidney (tenofovir, indinavir?, atazanavir?)●Bilirubin – liver ( X atazanavir)
Sensitive but not specific
Tests and monitoring in HIV infection
Kidney function
Urine dipstick test or blood test = first test and is indicative but inconclusive
Tests and monitoring in HIV infection
Kidney function
●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 pregnancy
Tests and monitoring in HIV infection
Kidney function
Different formulas to calculate GFR
http://en.wikipedia.org/wiki/Glomerular_filtration_rate
Tests and monitoring in HIV infection
C-reactive protein
Risk of diabetes, hypertension and CV disease
Low risk: <1mg/LHigh risk: >3mg/L
Drugs: PIs?, AZT?
C-reactive protein is a plasma protein produced by the liver (so, another blood test...)
Tests and monitoring in HIV infection
C-reactive protein
C-reactive protein is also marker of inflammation from infection but seems to be a reliable marker for CV disease in HIV regardless of HAART
http://gateway.nlm.nih.gov/MeetingAbstracts/102261383.html
Tests and monitoring in HIV infection
Liver enzymes
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 liver
Tests and monitoring in HIV infection
Liver enzymes
ALT (alanine aminotransferase)
Normal range 7-30 units/L W, 10-55 units/L M
May be more reliable sign of liver damage
Tests and monitoring in HIV infection
Liver enzymes
AST (aspartate aminotransferase)
Normal range 9-25 units/L W, 10-40 units/L M
Unreliable sign of liver damage
Pregnancy may decrease AST
Tests and monitoring in HIV infection
Liver enzymes
ALP (alkaline phosphatase)
Normal range 30-100 units/L W, 45-115 units/L M
Non-specific sign of liver damage
Atazanavir and indinavir can raise ALP
Tests and monitoring in HIV infection
Liver enzymes
GGT (gamma glutamyl transferase)
Normal range >50 units/L W, >65 units/L M
Can be specific sign of liver damage
Tests and monitoring in HIV infection
Liver enzymes
Interpretation requires experience and the whole picture
●ALP+ GGT normal = bone disease?●ALP+ GGT+ = bile ducts? liver damage?●10 x ALT/AST = viral hepatitis? ARVs?
Tests and monitoring in HIV infection
Liver enzymes
Bilirubin
Direct (unconjugated) 0-7 µmol/L Total 0-17 µmol/L
Bilirubin levels slightly higher in males than females, black Africans.
Drugs: atazanavir, indinavir
Tests and monitoring in HIV infection
Liver enzymes
Bilirubin
Jaundice clinically detectable at levels above 40 µmol/l.
Exception: with atazanavir (or ritonavir) if bilirubin levels around 60-70 µmol/l
Tests and monitoring in HIV infection
Liver enzymes
Bilirubin ++ jaundice
Other enzymes ++ may show no outward sign
Tests and monitoring in HIV infection
Liver enzymes
Q: what is the most liver-damaging over-the-counter (OTC) medicine?
Tests and monitoring in HIV infection
Liver enzymes
Q: what is the most liver-damaging over-the-counter (OTC) medicine?
A: Paracetamol
Tests and monitoring in HIV infection
Liver enzymes
WHO's top 10 liver-damaging medicines
Paracetamol, troglitazone, valproic acid, d4T, halothene, 3TC, ddI, amiodarone, nevirapine, cotrimoxazole
The ABCs of liver disease, Edwin J Bernard, NAMhttp://www.aidsmap.com/files/file1000630.pdf
Tests and monitoring in HIV infection
Liver
PT time – Prothrombin Time
Also called INR - International Normalized Ratio
Evaluate the ability of blood to clot properly
Not an enzyme test
Tests and monitoring in HIV infection
Liver
PT time – Prothrombin Time
Monitor anti-coagulants?, bleeding disorders, before surgery
Normal range 11-13.5 seconds1.5-2 times normal = too slow but no consensus on calibration of test as marker of over-fast clotting
Tests and monitoring in HIV infection
Liver
PT time – Prothrombin Time
INR = (Pt test
/ PT
normal) ISI
ISI = International Sensitivity Index for tissue factor (1-1.4)
Tests and monitoring in HIV infection
Anaemia
Iron, B12, B6, folic acid, red blood count, heamoglobin (HGB), mean corpuscular haemoglobin (MCH), heamocrit (HCT), mean corpuscular volume (MCV)
Drugs: AZT (pregnant?)
Tests and monitoring in HIV infection
Anaemia
Haemocrit
Normal ranges 40-52% M 35-35% W
Low haematocrit = anaemia?
Tests and monitoring in HIV infection
Anaemia
Haemoglobin
Normal ranges 11.5- to 16.5g W 13-18g M per 100mL blood
Low haemoglobin = anaemia?
Tests and monitoring in HIV infection
Anaemia
Mean corpuscular volume
Larger = anaemic, B6, B12, folic acid deficiency?
Smaller = anaemic, iron deficiency?
AZT (and smoking) can increase MCV without causing anaemia
Tests and monitoring in HIV infection
Anaemia
Red blood count (total erythrocytes)
Normal range 3.8-5 W 4.5-6.5 M billion per litre or million per cubic millimitre of blood (1012/L).
Low count = anaemia? but not sensitive or specific = probably a first test
Tests and monitoring in HIV infection
The rest...
Blood chemistryhttp://www.aidsmeds.com/articles/CSTest_4730.shtml
http://www.aidsmeds.com/articles/CBCTest_4729.shtml
A-Z testshttp://www.aidsmap.com/cms1031936.asp
http://www.labtestsonline.org.uk/
Hepatitis C coinfection – liver and diagnosishttp://www.i-base.info/guides/hepc/livertests.html
http://www.i-base.info/guides/hepc/hcvtesting.html
Tests and monitoring in HIV infection
Tests to avoid during pregnancy
● Amniocentesis● Chorionic villus sampling● Fetal scalp sampling● Cordocentis● Percutaneous umbilical cord sampling● Internal fetal labour monitoring (external ultrasound and fetal monitoring OK)
Tests and monitoring in HIV infection
Plebotomy (having blood taken)
A cruel and unusual punishment - or nice chat with the nurse?
Tests and monitoring in HIV infection
Blood count reference ranges
●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) 80-97
Tests and monitoring in HIV infection
Blood count reference ranges
CD4 400-1,600 per mm3
CD4% 32-68%
CD8 140-1000 per mm3
CD4:CD8 ratio 0.9-6
Tests and monitoring in HIV infection
Sampling
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
Results
One result is rarely conclusive
ANY unusual or unexpected results should ALWAYS be retested before making a
treatment decision
“Normal” is a difficult word – tests refer to reference ranges, can mean doctor/nurse is
happy with results even though high/low
Tests and monitoring in HIV infection
Sensitive v specific
Sensitivity = reacts positively
Specificity = reacts positively in right circumstances
Tests and monitoring in HIV infection
Sensitive v specific
Sensitivity = rule in Sensitivity refers to the proportion of people with disease who have a positive test result
Specificity = rule outSpecificity refers to the proportion of people without disease who have a negative test result.
Tests and monitoring in HIV infection
Sensitive v specific
SnNout: when a sign, test or symptom has a high Sensitivity, a Negative result rules out the diagnosis.
SpPin: when a sign, test or symptom has a high Specificity, a Positive result
rules in the diagnosis.