MASANGA HAEMOZOIN BIOSENSOR TRIALCIARÁN DOHERTY

Masanga HospitalA rural compound, providing free healthcare in paediatrics, maternity, general medicine and surgery in Tonkolili district, Sierra Leone.

Staffed largely by local auxilliaries, Dutch doctors and British & Danish volunteers.

Sierra LeoneLocation: West Africa

Population: 6 million

Infamous for the brutal civil war between ‘91 & ‘02, the country is now at peace, although still remains one of the poorest in the world

Malaria in Sierra Leone• Malaria is the 5th largest cause of death by infectious

disease worldwide, accounting for around 200 million cases per year and up to 1 million deaths

• 100% of Sierra Leone is classed as a high transmission zone

• 10,000 cases of malaria were confirmed per every 100,000 people in 2010

• Malaria is a major contributor to Sierra Leone having the 4th lowest life expectancy and 2nd highest infant mortality in the world (below only Afghanistan)

Haemozoin

• All species of the malaria parasite Plasmodium metabolise haemoglobin and excrete the toxic iron molecules as an inert crystal

• These crystals, known as haemozoin, are both magnetic and dichroic, meaning they absorb different polarisations of light in different amounts

Haemozoin

Exeter Team

A team of physicists and engineers at the University of Exeter came together to produce a device that could detect haemozoin in the blood

Haemozoin Biosensor• Aka. MOT (Magneto-Optic Test)

• The MOT detects the presence of haemozoin crystals by applying a magnetic field to a sample of infected blood, aligning them all in the same plane and then shining a polarised light across them

• A sensor at the other end detects changes in light absorption

• The diagnosis of malaria is made on the presumption that the haemozoin it detects is as a result of active infection

Original MOT

The first MOT device developed

Current Prototype

The handheld, portable MOT

What diagnostics are available?

Rapid Diagnostic Tests (RDTs)

• Cheap and easy to use

• Sensitivity/specificity varies according to brand

• Must be stored in cool, dry environment

• Non-reusable

Microscopy

• Gold standard

• Can differentiate species and give detail on gametocytes, parasitaemia etc.

• Expensive (labor time)

• Requires high level of training + equipment

Rapid Diagnostic Tests (RDTs)

Why test for haemozoin?• Present in the blood only during active infection, unlike

antibodies

• Requires just a pinprick of blood

• Quicker: takes just 30 seconds

• Cheaper: initial cost of machine only

• Easier: requires no expert training, gives a simple yes/no diagnosis of malaria

• No special storage requirements

Objectives• Test 300 patients with ?malaria on the MOT

• To compare these results against both microscopy, two brands of RDT, and in cases of discrepancy, PCR

• Derive sensitivity and specificity values from the data

• As a side project, evaluate the difference in sensitivity and specificity of the two RDT brands in order to identify possible weaknesses in pre-existing rapid diagnostics

Our lab…

Biosensors

Power supply

Sample prep

PCR prep

Results• MOT data under non-disclosure agreement… Data

currently being analysed and will be published in 2012/13

• RDT comparison study showed significant differences between the two brands, with some sacrificing specificity for higher sensitivity and vice versa

• Hospital ran out of their own RDTs mid-way through trial, highlighting the impracticality of disposable tests in poor, rural settings

As an elective…

Any questions?