Question 1 [13 marks]

Purified protein sample ‘X’ was used to plot a standard curve for an assay to measure antibodies in patients’ blood samples. Sample ‘X’ was serially diluted and absorbance was measured for each concentration (Table 1).

a) Why was ‘0’ concentration of stock solution used in this test (last row)? Justify your answer. [3 marks]

b) Using the data from Table 1, plot a standard curve. [7 marks]

c) A patient’s blood sample was diluted 100 times and it produced an absorbance reading of 0.5. What is the concentration of antibody in the patient’s blood? [3 marks]

Question 2 [10 marks]

Test A is a gold standard method to determine disease ‘X’. Two other new test methods, B and C were compared with Test A. A method evaluation was done using Bland-Altman plots. The graphs are shown below.

a) Analyse the charts plotted and conclude if the new tests (Test B and C) are suitable to replace the gold standard (Test A). Provide relevant justifications for your conclusion. [6 marks]

b) It is reported that Test A has a sensitivity of 98% and specificity of 75%. Is Test A more suitable to be used as a screening test or as a confirmatory test? Justify your answer. [4 marks]

Question 3 [17 marks]

The following video shows the features of an automated slide stainer.

Laboratory XYZ, decided to purchase this slide stainer.

A. Outline the steps required to conduct a break-even analysis for these instruments. Discuss the importance of conducting break-even analysis before purchasing such devices. [4 marks].

B. State TWO analytical errors that might occur while using this instrument. Explain how to minimize them. [4 marks]

C. Identify THREE work activities and draft a Hazard Identification and Risk Assessment (HIRA) document for the automated slide stainer. Please use the template provided below. [9 Marks]