2. Introduction
• Leuser Virus also known as the yellow eye disease.
• It has been emerging in South-East Asia in the past few
months..
• 2 emerging strains, strain 1 (wild type), strain 2 (lethal)
• Symptoms: yellow eye, mild flu-like symptoms
however if untreated it can cause a sudden rapid
decline and death.
• Diagnostic ELISA-based blood test.
• ELISA is very expensive and pick up both strains of the
virus, so it can’t distinguish between the two strains.
• The aim of this report is to develop a yellow-eye
diagnostic assay based on enzyme X, and to whether
the assay is a good candidate for full clinical
evaluation.
- Optimisation of assay (pH, temperature, wavelength, incubation
time).
- Determination of clinical cut-offs for the assay, to distinguish
patients infected with strain 2.
4. Results
Figure 1- Figure Showing the concentration of enzyme X
against the absorbance.
Known
concentration
(mg/L)
Measured
concentration
(mg/L)
QC1 5 0.620
QC2 2.57 0.342
Quality control measured
concentration (mg/L)
5. Results
Figure 2- Figure showing the standard curve for patient set A
against the absorbance.
Cut-off
concentration
=0.4
6. Results
2 X 2 table for cut-off 0.4
Figure 3- Figure showing the standard curve for patient set B
against the absorbance. Bellow the cut-off shows strain 1 (mild)
and above the cut-off shows strain 2 (lethal).
Cut-off
concentration
= 0.4
Strain 1 Strain 2
Positive 21(true +) 2 (false +)
Negative 2 (false - ) 15 (true - )
False
positives = 2
False
negatives= 2
7. Clinical sensitivity and specificity was calculated:
• 91% sensitivity- The proportion of patients with
the strain 1 were correctly identified by the test.
• 88% specificity- The proportion of patients without
strain 1 (meaning strain 2) were correctly identified
by the test.
Post Test Likelihood
PPV 91%
NPV 88%
Table 2. Post Test Likelihood– Positive and
negative predictive values
• PPV- 91% likelihood of
patients having strain 1.
• NPV- 88% likelihood of
patients not strain 1
• Lower NPV as there was
a lower specificity value
8. Conclusion
• Low number of false negatives (2) =
High sensitivity
• Low number of false positives (2) =
High specificity
• Clinical sensitivity (91%) and clinical
specificity (88%) confirmed and
validated enzyme assay reliability.
• These results have proven to be
considered for future investigations
and relevant for the development of
enzyme X assay-based diagnostic for
detection of leucer virus.
Limitations
• Low QC values- enzyme X assay
was not accurate
- triplicates, to limit the freeze-thaw
cycles. .
