Blood Sciences
Interpretative assignment 2015-16
A 19 year-old woman, patient M, has been diagnosed with infectious mononucleosis an infectious viral disease characterized by swelling of the lymph glands and prolonged lassitude by her GP. The diagnosis was confirmed by blood tests. Three weeks later she returned to her GP feeling very unwell. When examined she presented with symptoms of mild jaundice yellow discoloration of the skin caused by increase levels of billirubin. On examination there was tenderness in the right upper abdominal quadrant but the liver was not palpable. The GP took some blood and sent it for testing.
Question 1
Discuss the typical laboratory results expected for haematological investigations in a case of infectiousHow is it used?
The Monospot test is used to determine whether you have infectious mononucleosis. This test is rapid and easy to perform, but it is not 100% specific. More testing may be needed to confirm that the disease is mononucleosis and not another illness.
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When is it requested?
The Monospot test is requested if your doctor suspects that you have infectious mononucleosis, which causes fever, headache, swollen glands, tiredness, and malaise. Your healthcare professional may detect that you have an enlarged spleen or liver.
The test will not be positive until you have been infected for about two weeks. Other tests may need to be requested if the heterophil antibodies are negative, but your doctor still suspects mononucleosis as the cause of your symptoms.
Other blood tests that are more specific to the EBV can be used to find early infection or to confirm mononucleosis. These tests include the IgM and IgG antibodies to the viral capsid antigen (VCA), which can be found early in the disease. VCA IgM is only present in the few weeks after infection, but the IgG antibodies can also be found later, during the patient's recovery. Antibodies to Epstein-Barr virus Nuclear Antigen (EBNA) may also be tested for to gain a more accurate indication of recent or previous EBV infection.
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What does the test result mean?
A positive result in the Monospot test, together with symptoms of mononucleosis, are the basis for a diagnosis of infectious mononucleosis. In addition to a positive reaction on the Monospot test, an infected person has a higher white blood cell count, with a higher than usual number of atypical lymphocytes. Heterophil antibodies decline after the fourth week of illness, and the Monospot test will become negative as the infection resolves.

A negative test result means that a person may not have mononucleosis or that it is too early in the illness to detect the antibodies. The test may need to be repeated if symptoms remain. Infants and young children do not make heterophil antibodies when infected with EBV, so more specific viral tests must be used to make the diagnosis.
Interpretation of Specific EBV Test results EBV IgM antibody | EBV IgG antibody | EBNA antibody | Interpretation | Positive | Negative | Negative | Recent EBV infection | Positive | Positive | Negative | Recent EBV infection | Negative | Positive | Positive | Previous EBV infection |
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Is there anything else I should know?
In young adults, an effective laboratory diagnosis can be made on a single blood sample during the acute phase of the disease with a Monospot test. By requesting the more extensive battery of EBV blood tests, the healthcare professional will be able to learn whether a person is susceptible to EBV, has had a recent infection, has had EBV infection in the past, or has a reactivated EBV infection.

When the Monospot test is negative, a combination of EBV antibody tests for IgM and IgG to the viral capsid antigen, IgM to the early antigen, and IgG antibody to the nuclear antigen may be requested, as well as antibody tests for cytomegalovirus (CMV) or Toxoplasma gondii. mononucleosis. Link the findings to the pathophysiology of this disease.

Pathophysiology[edit]
The virus replicates first within epithelial cells in the pharynx (which causes pharyngitis, or sore throat), and later primarily within B cells (which are invaded via their CD21). The host immune response involves cytotoxic (CD8-positive) T cells against infected B lymphocytes, resulting in enlarged, atypical lymphocytes (Downey cells).[20]
When the infection is acute (recent onset, instead of chronic), heterophile antibodies are produced.[10]
Cytomegalovirus, adenovirus and Toxoplasma gondii (toxoplasmosis) infections can cause symptoms similar to infections mononucleosis, but a heterophile antibody test will test negative and differentiate those infections from infectious mononucleosis.[2][21]
Mononucleosis is sometimes accompanied by secondary cold agglutinin disease, an autoimmune disease in which abnormal circulating antibodies directed against red blood cells can lead to a form of autoimmune hemolytic anemia. The cold agglutinin detected is of anti-i specificity.[22][23]

http://labtestsonline.org.uk/understanding/analytes/mono/tab/test/#what https://www.msdmanuals.com/en-gb/professional/infectious-diseases/herpesviruses/infectious-mononucleosis (20 marks)
Question 2
For each parameter in Table 1, briefly explain the underlying biochemistry and how it may be used to contribute to a clinical diagnosis. (25 marks) Table 1: results from the analysis of serum taken from patient M | Parameter | Value | Total protein (g/L) | 61 | Albumin (g/L) | 29 | Total bilirubin (µmol/L) | 57 | Direct bilirubin (µmol/L) | 7 | Aspartate transaminase (AST) (U/L) | 128 | Alanine transaminase (ALT) (U/L) | 215 | Alkaline phosphatase (ALP) (U/L) | 425 | Gamma glutamyl transferase (γGT) (U/L) | 121 | Prothrombin time (PT) (sec) | 19 |

Question 3
Table 2 shows the quality control data for the assays run to determine values for some of the parameters in Table 1. With reference to the expected values given for the QC for each parameter, and showing your workings, determine whether each assay is valid. (15 marks)

Table 2: quality control values | | Parameter | Measured | Expected | Total protein (g/L) | 42.3 | 45.5 | Albumin (g/L) | 31.5 | 27.0 | Total bilirubin (µmol/L) | 94.6 | 91.5 | Direct bilirubin (µmol/L) | 29.8 | 31.2 | Aspartate transaminase (AST) (U/L) | 139 | 150 | Alanine transaminase (ALT) (U/L) | 83 | 80 | Alkaline phosphatase (ALP) (U/L) | 118 | 120 | Gamma glutamyl transferase (γGT) (U/L) | 119 | 135 |

Question 4
Considering the data for patient M, and referring to the reference ranges for the parameters shown in Table 3, comment on the value of each parameter for the patient as to whether it is a cause for concern. (10 marks) Table 3: reference ranges | Parameter | Value | Total protein (g/L) | 60-80 | Albumin (g/L) | 35-50 | Total bilirubin (µmol/L) | 2-20 | Direct bilirubin (µmol/L) | <7 | Aspartate transaminase (AST) (U/L) | 10-50 | Alanine transaminase (ALT) (U/L) | 5-42 | Alkaline phosphatase (ALP) (U/L) | 30-150 | Gamma glutamyl transferase (γGT) (U/L) | 5-55 | Prothrombin time (PT) (sec) | 13-16 |

Question 5
Briefly explain the connection between a diagnosis of IM and possible effects on the liver. (10 marks)
Questions 6
For the three dye-binding assays, reagent blanks were used for the determination of total protein by Biuret and albumin by Bromocresol Green. However sample blanks were used for the measurement of bilirubin by the Jendrassik-Grof method. Explain the difference between the two types of blanks and why they are used. (10 marks)
Question 7
From the symptoms displayed by the patient on presentation suggest an alternative diagnosis that could be given and explain how laboratory testing can contribute to a differential diagnosis. (10 marks)