Viral load (VL) testing

Clinical description

• VL is the best test to monitor success/failure of ART

o VL = number of viral particles per ml of blood.

o More virus  faster destruction of CD4 cells  more severe immunosuppression

• The VL monitoring schedule is designed to detect adherence problems and potential ART failure early

while avoiding unnecessary tests to save cost.

• Collect the first scheduled VL 6 months after starting ART. Normally, patients are expected to have an

undetectable VL at this time. If the VL is detectable, possible causes are:

o Most likely a sign of poor adherence.

o Patients who were infected with drug-resistant HIV.

o Patients who developed drug-resistance from previous ARV use (e.g., infants who received NVP prophylaxis).

• Patients who have suppressed viral load at 6 months and are adherent and clinically well have a low risk

of ART failure. Therefore, routine VL monitoring is scheduled approximately every 12 months.

• Children on paediatric regimens, pregnant and breastfeeding women require 6 monthly VL monitoring

because a high VL is common in these groups and has severe implications.

• Collect missed VL tests at the next regular visit.
• Do additional targeted VL tests outside of this schedule when suspecting ART failure.
• Explain the standard VL monitoring schedule to every patient. Ask the patient to help remember when

VL is due.

o Explain (example): “You had your viral load drawn in November. Therefore, every November ASK your provider for your viral load test to be done.”

• Actively communicate (phone / home visit) any detectable VL results (above detection limit, even if

<1000) to patients as soon as the result is received at the site. Call for an early appointment.

• DBS and plasma VL samples produce different results in the low ranges below 839 copies/ml:

o DBS results are usually not quantifiable below 839 copies/ml. (Some labs may produce an actual readout above 400 copies/ml from DBS). A DBS result <839 copies/ml means that some viruses have been detected, but it is not possible to determine if this VL is in the very low range below 200 copies/ml or higher.

o Plasma results are usually quantified above 40 copies/ml.

o Both DBS and plasma results of <LDL mean that no virus has been detected, i.e., the VL is undetectable or fully suppressed.

o Plasma is the gold-standard for viral load testing. Collect plasma samples if feasible.

Continuing ART

• ARV drug resistance starts gradually with low level viraemia for many months. Emerging drug-

resistant virus does not cause any immediate clinical symptoms.

• HIV will grow resistant to more and more ARVs if a patient continues to take a failing ART

regimen for several months. Accumulated multiple ARV resistance can make it difficult to find a second- or third-line regimen that still works.

• Although DTG has a high barrier to resistance development, some cases with DTG resistance

have emerged.

• HIV drug resistance usually affects different ARVs of the same class (cross resistance).
• Example: HIV that has grown resistant to EFV will also be resistant to NVP, even if the patient

has never taken NVP before.

• Drug resistant virus can be transmitted to other people.