Collection of DBS samples for EID and VL

Clinical description

• Diagnosing HIV infection in infants and detecting treatment failure in patients on ART is done

by testing for HIV genetic material in a blood sample.

• This requires making millions of copies of the genetic material so that there is enough to be

measured. This method is called polymerase chain reaction (PCR). PCR is very sensitive and it can be disturbed by tiny amounts of dirt or contact with other samples.

• PCR testing is only done in special labs, making it necessary to prepare dried blood spot (DBS)

samples that can be kept at normal temperature for several weeks.

• Carefully follow the protocol when preparing DBS samples. Most steps are the same, but there

are some important differences between DBS for EID and VL (shown below). VL can also be tested using plasma samples.

• Never allow EID samples to touch or mix with VL samples as this will lead to false positive EID

results:

o Use separate rooms or at least separate tables within one room.

o Allocate different staff for collection of DBS for EID and VL.

o Use separate drying racks, clearly labelled EID and VL.

• Pack DBS for EID and VL in separate plastic bags and envelopes.

Table 8: Summary protocol for preparation of DBS samples for EID and VL Early Infant Diagnosis (EID) Viral Load (VL) Caution Getting • Label DBS card with patient name, ID and date • Hold the filter paper card only at the edges ready • Wash hands, put on gloves, wash powder off gloves (unless powder-free) • Never touch the area near the circles Sample • Infants <9kg: select left or right side of the sole under the heel collection • Children under 2 years >9kg: select heel or side of big toe

• From age 2 years and adults: select side of fingertip, preferably ring finger
• Position down, warm up, squeeze intermittently
• Wipe with alcohol swab, dry for 30 sec • Avoid excessive squeezing of heel / toe / finger
• Press lancet on skin, prick, dispose into sharps bin
• Wipe away first drop of blood with sterile gauze, wait for large drop of blood to appear
• Drip one free drop of blood directly onto • Dip capillary into blood drop and fill to • Don’t allow the finger / toe to touch the filter

filter paper black line (50 micro litres) paper

• Hold tip of the capillary at a slight angle in • Apply blood only on one side of filter paper

the centre of the circle on the filter paper • Don’t rub or scratch filter paper with capillary

• Let the blood soak into the paper to fill the whole circle • Don’t re-apply more blood to the same circle
• Repeat this procedure until all 5 circles are filled

Drying • Slot filter paper into drying rack • Don’t touch/ smear/ allow to touch other objects

• Dry in protected area at room temperature for at least 3 hours (best overnight) • Protect from sunlight, heat, dust, insects, rodents

Packing • Put each filter paper card into a separate zip-lock bag • Don’t pack filter paper cards before completely

• Put 3 sachets with desiccant into each zip-lock bag dried

Standard monitoring of HIV patients

• Squeeze out air and seal zip-lock bag • Don’t combine EID and VL samples in same
• Use marker pen to label the zip-lock bag and envelope, including ‘EID’ or ‘VL’ envelope
• Insert zip-lock bags and specimen forms in this envelope and seal

Storage, • Store envelopes in cool dry place • Keep away from sunlight transport