Tests and monitoring in HIV infection

1
Tests and monitoring in HIV infection

• UK standard of care and some other useful tests
• Matthew Williams
• UK CAB

2
Tests and monitoring in HIV infection

• UK standard of care and some other useful tests

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Tests and monitoring in HIV infection

• CD4 count
• Viral load
• Resistance
• Therapeutic drug monitoring

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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.

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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.

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Tests and monitoring in HIV infection

• CD4 count
• CD4 lt200 greater risk of opportunistic
  infections (OIs) AIDS threshold for
  prophylaxis eg for PCP bottom of UK threshold
  for starting combination therapy
• CD4 lt50 very great risk of OIs

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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)

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Tests and monitoring in HIV infection

• CD4 count
• CD4 count lower in pregnancy temporary drop of
  50 cells/mm3

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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

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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.

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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

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Tests and monitoring in HIV infection

• Viral load
• When you are on HIV treatment, your viral load
  should be reduced to undetectable lt50
  copies/mL 1.7 log10

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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

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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)

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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

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Tests and monitoring in HIV infection

• Resistance test

Resistance test
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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

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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 (lt1 log10 copies/mL drop in
  viral load by 48 weeks) should prompt resistance
  testing at that time.
• BHIVA, Treatment of HIV-infected adults with
  antiretroviral therapy (2006)

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Tests and monitoring in HIV infection

• Resistance test

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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

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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/

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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.ht
  ml

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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 lt1log10
  after 4-8 weeks after starting HAART, (genotype)
• iv) after virological failure

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Tests and monitoring in HIV infection

• UK standard of care
• BHIVA viral load before and 4-8 weeks after
  starting treatment (as necessary thereafter)

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Tests and monitoring in HIV infection

• UK standard of care
• BHIVA CD4 count before treatment (as necessary
  thereafter)

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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

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Tests and monitoring in HIV infection

• UK standard of care and some other useful tests

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Tests and monitoring in HIV infection

• Liver enzymes
• Kidney function
• Urine
• Albumin
• Bone density
• Glucose
• Platelets
• Red blood count
• White blood count
• Lipids

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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

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Tests and monitoring in HIV infection

• Tests blood, blood and more blood...
• Many tests require a blood sample

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Tests and monitoring in HIV infection

• Blood glucose
• Blood cholesterols and triglycerides
• Kidney function
• C-reactive protein
• Liver enzymes
• Anaemia
• Lactic acidosis

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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?

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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

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Tests and monitoring in HIV infection

• Blood cholesterols and triglycerides
• Total cholesterol
• Target level under 5.2 µmol/L (4-6.4 µmol/L)

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Tests and monitoring in HIV infection

• Blood cholesterols and triglycerides
• LDL cholesterol
• Target level under 3.4 µmol/L

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Tests and monitoring in HIV infection

• Blood cholesterols and triglycerides
• HDL cholesterol
• Target level over 0.9 µmol/L

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Tests and monitoring in HIV infection

• Blood cholesterols and triglycerides
• Cholesterol CV risk cannot be judged on
  cholesterol levels alone, HDLLDL ratio,
  lifestyle, BMI, age and other factors are
  important
• Smoking!

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Tests and monitoring in HIV infection

• Blood cholesterols and triglycerides
• Triglycerides
• Fasted levels lt2.2 µmol/L normal, 2.24.4 µmol/l
  borderline, gt11 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

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Tests and monitoring in HIV infection

• Urine
• Dipstick test
• Protein kidney (tenofovir) ltlt mostly albumin
• Glucose insulin resistance (PIs), kidney
  (tenofovir, indinavir?, atazanavir?)
• Bilirubin liver ( X atazanavir)
• Sensitive but not specific

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Tests and monitoring in HIV infection

• Kidney function
• Urine dipstick test or blood test first test
  and is indicative but inconclusive

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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

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Tests and monitoring in HIV infection

• Kidney function
• Different formulas to calculate GFR
• http//en.wikipedia.org/wiki/Glomerular_filtration
  _rate

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Tests and monitoring in HIV infection

• C-reactive protein
• Risk of diabetes, hypertension and CV disease
• Low risk lt1mg/L
• High risk gt3mg/L
• Drugs PIs?, AZT?
• C-reactive protein is a plasma protein produced
  by the liver (so, another blood test...)

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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/102261
  383.html

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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

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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

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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

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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

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Tests and monitoring in HIV infection

• Liver enzymes
• GGT (gamma glutamyl transferase)
• Normal range gt50 units/L W, gt65 units/L M
• Can be specific sign of liver damage

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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?

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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

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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

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Tests and monitoring in HIV infection

• Liver enzymes
• Bilirubin jaundice
• Other enzymes may show no outward sign

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Tests and monitoring in HIV infection

• Liver enzymes
• Q what is the most liver-damaging
  over-the-counter (OTC) medicine?

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Tests and monitoring in HIV infection

• Liver enzymes
• Q what is the most liver-damaging
  over-the-counter (OTC) medicine?
• A Paracetamol

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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, NAM
• http//www.aidsmap.com/files/file1000630.pdf

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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

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Tests and monitoring in HIV infection

• Liver
• PT time Prothrombin Time
• Monitor anti-coagulants?, bleeding disorders,
  before surgery
• Normal range 11-13.5 seconds
• 1.5-2 times normal too slow but no consensus on
  calibration of test as marker of over-fast
  clotting

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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)

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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?)

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Tests and monitoring in HIV infection

• Anaemia
• Haemocrit
• Normal ranges 40-52 M 35-35 W
• Low haematocrit anaemia?

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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?

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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

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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

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Tests and monitoring in HIV infection

• The rest...
• Blood chemistry
• http//www.aidsmeds.com/articles/CSTest_4730.shtml
  
• http//www.aidsmeds.com/articles/CBCTest_4729.shtm
  l
• A-Z tests
• http//www.aidsmap.com/cms1031936.asp
• http//www.labtestsonline.org.uk/
• Hepatitis C coinfection liver and diagnosis
• http//www.i-base.info/guides/hepc/livertests.html
  
• http//www.i-base.info/guides/hepc/hcvtesting.html
  

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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)

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Tests and monitoring in HIV infection

• Plebotomy (having blood taken)
• A cruel and unusual punishment - or nice chat
  with the nurse?

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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

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Tests and monitoring in HIV infection

• Blood count reference ranges
• CD4 400-1,600 per mm3
• CD4 32-68
• CD8 140-1000 per mm3
• CD4CD8 ratio 0.9-6

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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...

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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

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Tests and monitoring in HIV infection

• Sensitive v specific
• Sensitivity reacts positively
• Specificity reacts positively in right
  circumstances

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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 out
• Specificity refers to the proportion of people
  without disease who have a negative test result.

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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.

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Tests and monitoring in HIV infection

• Sensitive v specific
• Many rapid tests are highly sensitive but not
  specific enough to be definitive prone to
  sample contamination
• Urine dipstick tests
• Fingerprick tests