Leapfrog diagnostics: Demonstration of a broad spectrum pathogen identification platform in a resource-limited setting.

BACKGROUND: Resource-limited tropical countries are home to numerous infectious pathogens of both human and zoonotic origin. A capability for early detection to allow rapid outbreak containment and prevent spread to non-endemic regions is severely impaired by inadequate diagnostic laboratory capacity, the absence of a "cold chain" and the lack of highly trained personnel. Building up detection capacity in these countries by direct replication of the systems existing in developed countries is not a feasible approach and instead requires "leapfrogging" to the deployment of the newest diagnostic systems that do not have the infrastructure requirements of systems used in developed countries. METHODS: A laboratory for molecular diagnostics of infectious agents was established in Bo, Sierra Leone with a hybrid solar/diesel/battery system to ensure stable power supply and a satellite modem to enable efficient communication. An array of room temperature stabilization and refrigeration technologies for reliable transport and storage of reagents and biological samples were also tested to ensure sustainable laboratory supplies for diagnostic assays. RESULTS: The laboratory demonstrated its operational proficiency by conducting an investigation of a suspected avian influenza outbreak at a commercial poultry farm at Bo using broad range resequencing microarrays and real time RT-PCR. The results of the investigation excluded influenza viruses as a possible cause of the outbreak and indicated a link between the outbreak and the presence of Klebsiella pneumoniae. CONCLUSIONS: This study demonstrated that by application of a carefully selected set of technologies and sufficient personnel training, it is feasible to deploy and effectively use a broad-range infectious pathogen detection technology in a severely resource-limited setting.

Microcomputer evaluation of cerebral blood flow velocity studies in the neonate.

A semi-automated system for evaluation of Doppler cerebral blood flow studies obtained from newborn infants is described. A low cost digitizer is used to convert the graphic data from the flow tracing to digital data. A small business computer is used to analyze the data and produce a chartable report. The reliability of the digitizer is also evaluated.

Relationships of five Doppler measures with flow in an in vitro model and clinical findings in newborn infants.

This report compares six Doppler ultrasound measures of blood flow: Pourcelot's pulsatility index, Gosling's pulsatility index, area under the curve, systolic amplitude, diastolic amplitude, and mean amplitude. Recordings from an in vitro arterial model and from the anterior cerebral arteries in 33 newborn infants with asphyxia, intraventricular hemorrhage, or normal state were analyzed. In the model, all measures had excellent correlation with flow. Neonates were correctly classified according to diagnosis by the Doppler measures as follows: Pourcelot's pulsatility index (100%), Gosling's pulsatility index (97%), diastolic amplitude (94%), mean amplitude (76%), area under the curve (70%), and systolic amplitude (58%). The best accuracy was obtained with the pulsatility indices.

The use of a microcomputer in the evaluation of echocardiograms.

A low-cost microcomputer system is used to calculate cardiac parameters from echocardiographic (Echo) measurements and produce a chartable report. The system is simple, uses Basic language, and provides for data storage.

The fontanelle tonometer: a noninvasive method for measurement of intracranial pressure.

The use of a modified pneumotonometer as a noninvasive method to measure intracranial pressure through the fontanel was evaluated in the animal laboratory and in the clinical setting. Pressure measured with the tonometer from a surgically created fontanel in an adult mongrel dog demonstrated good correlation with pressure measured from an epidural balloon catheter. Pressure recorded with the tonometer was compared with direct measurements in a single infant. There were 20 paired measurements with a correlation coefficient of 0.91. Fontanel pressure was measured in 72 healthy infants. The mean pressure was 7.0 mm Hg with a standard deviation of 1.75. This result compares favorably with previous reports utilizing other methods. The machine is safe and simple to use.

Intracranial pressure and cerebral arterial pulsatile flow measurement in neonatal intraventricular hemorrhage.

We examined the clinical significance of noninvasive intracranial pressure measurements and pulsatility indices in 74 infants with confirmed IC-IVh. The intracranial pressure measurements were obtained using the applanation principle, and the pulsatility indices were calculated from the Doppler flow velocity tracings of the anterior cerebral artery. Fifty-three infants (71.6%) who died had a significantly lower birth weight and gestational age than those who survived. Survival rate decreased significantly with increased intracranial pressure (P less than 0.0002) and increased pulsatility indices (P less than 0.0001). We found no significant relationship between outcome and the size of IC-IVH demonstrated by CT scan. Birth weight, intracranial pressure measurements, and cerebral arterial pulsatile flow changes appear to be major prognostic indicators in neonatal IC-IVH.