Jack is a 12-year-old student who came to the clinic because of stomach pain, nausea, and vomiting. His symptoms started three days ago with loss of appetite, headache, and a mild fever. Now he feels very ill, has not been able to eat for three days and only drank a cup of water today. His urine is dark, and his stool is light brown. He has no significant illness in his medical history and does not take any medication regularly. On examination:

• Height: 147 cm, Weight: 43 Kg, BMI: 19.9 (77^th percentile)
• BP: 112/64 mmHg, Heart rate: 98/min, Respiratory rate: 24/min, Temperature: 37.3°C, O₂ SAT: 98%
• Appears ill and lethargic.
• Dry skin and mucous membranes. Yellow discoloration of sclera. Liver can be palpated at the right costal margin.

Considering the yellow colour of Jack’s eye, the dark urine, and the light brown stool, what specific laboratory tests should be ordered?

Jack's laboratory investigation showed:

• Blood analysis:
  • CBC:
    • RBCs: 4.7 x 10¹²/ L, Hemoglobin: 160 g/L, Hematocrit: 0.43,
    • MCV: 92 fL, MCH: 33 pg, RDW: 12%, Reticulocytes: 0.9%, ESR: 21 mm/hour,
    • WBC: 7 x 10⁹/l, (Neutrophils: 3.4 x 10⁹/L, Lymphocytes: 6.3 x 10⁹/L, Basophils: 0.09. x 10⁹/L, Eosinophils: 0.45 x 10⁹/L, Monocytes: 0.8 x 10⁹/L),
    • Platelet counts: 260 x 10⁹/L
  • Na: 140 mmol/L, K: 4.3 mmol/L,
  • Glucose: 4.0 mmol/L, Creatinine: 99.2 umol/L, Uric Acid: 196 mmol/L
  • Triglycerides: 1.2 mmol/L, Cholesterol: 4.3 mmol/L, LDL: 2.2 mmol/L, HDL: 1.2 mmol/L
  • Total bilirubin: 95 umol/L, conjugated bilirubin: 19umol/L
  • AST: 645 U/L, ALT: 834 U/L, ALP: 217 IU/L, GGT: 92 IU/L, 5'-NT: 28 IU/L, Albumin: 45 g/L, LDH: 200 U/L
  • INR: 1.0
  • Vitamin B₁: 8.8 umol/L, Iron: 27 umol/L, Ferritin: 200 pmol/L, Copper: 12 umol/L, Folic acid: 4.31 nmol/ml
  • Alpha fetoprotein: 10 mg/L
  • Viral serology: HBsAg, HCV Ab, anti-HAV IgG: negative, anti-HAV IgM: positive, EBV, CMV negative
• Stool analysis: color: light brown, urobilin: +
• Urine analysis: color: dark, pH: 5.9, specific gravity: 1014, osmolarity: 547 mosmol; glucose, ketones: negative, bilirubin: ++, urobilinogen: ++, bile salts: positive, WBCs and RBCs: 1-3 and 0/HPF respectively, squamous epithelial cells, casts, bacteria, yeast: negative.

After looking at the laboratory results, what is your diagnosis?

Have a look at the virus serology results again:

• HBsAg, HCV Ab, anti-HAV IgG: negative, anti-HAV IgM: positive, EBV, CMV, VCA negative

  What does the anti-HAV IgM positivity indicate?

All the followings are characteristic to hepatitis A virus infection, EXCEPT: