Clinical Chemistry and Hematology
What the exam expects
This domain combines analyte interpretation with blood cell analysis. Expect questions on renal, hepatic, cardiac, and endocrine markers, electrolyte and acid-base disorders, lipid and glucose testing, and on complete blood count parameters, anemia classification, and coagulation. The goal is to interpret patterns rather than memorize single values.
Concepts to master
Understand the anion gap and its use in metabolic acidosis, the relationship between sodium and water balance, and how osmolality is estimated. Know liver enzyme patterns (hepatocellular versus cholestatic), cardiac troponin interpretation, and thyroid hormone relationships. In hematology, know red cell indices and how they classify anemia, the meaning of reticulocyte count, and the interpretation of platelet count and coagulation tests such as PT/INR and aPTT. Understand how preanalytical factors such as hemolysis or prolonged tourniquet time alter results.
Traps
Distractors often present a plausible but wrong anemia classification, or confuse the intrinsic and extrinsic coagulation pathways. Acid-base questions may tempt you to skip compensation checks. Watch for questions where a normal total calcium masks an abnormal ionized value, or where a delta gap is needed.
Worked example
A patient with metabolic acidosis has Na 140, Cl 100, and HCO3 14 mmol/L. Anion gap = 140 − (100 + 14) = 26, indicating a high-anion-gap acidosis. Always verify whether respiratory compensation is appropriate before finalizing the interpretation.