Raw–Factory–Loss

if low - where is the problem?

Common Things Are Common Think Horse, Not Zebra Day-1 House Officer Ready
The Core Principle

CTAC — Common Things Are Common

The rule Before thinking outside the box … make sure you master what's inside the box.
The metaphor When you hear hoofbeats — think horse, not zebra.
Your day-1 job Recognise common diseases. Interpret common lab abnormalities. Think logically and safely.

The Raw–Factory–Loss Model

Whenever something in the blood is low — ask only three questions

01

Is there a Raw material problem?

Raw Material
02

Is there a Factory problem?

Factory
03

Is it being Lost or destroyed?

Loss / Destruction

Applies to: Albumin · Haemoglobin · Platelets · Clotting Factors

01

Hypoalbuminaemia — Albumin is made in the liver from dietary protein

Protein-energy malnutrition
Poor dietary intake
In children → malnutrition is more common than rare liver enzyme defects.
Chronic liver disease
Acute liver failure
Mechanism The liver cannot synthesise albumin. Look for other signs of liver failure — coagulopathy, jaundice, encephalopathy.
Nephrotic syndrome
Protein-losing enteropathy
Severe burns
Child with oedema + low albumin → think nephrotic syndrome first.
02

Anaemia — Hb needs Iron, B12, Folate, healthy marrow & normal RBC survival

Iron deficiency anaemia
B12 deficiency
Folate deficiency
Microcytic anaemia in a child → iron deficiency is the horse.
Aplastic anaemia
Bone marrow infiltration
Leukaemia (e.g. Acute Lymphoblastic Leukaemia)
Key clues Pancytopenia · Low reticulocyte count (the factory has failed — no compensatory output)
Acute blood loss
Haemolysis
Thalassaemia (e.g. Beta-thalassaemia)
Key clues Reticulocytosis (marrow compensating) · Jaundice if haemolysis · Elevated LDH & unconjugated bilirubin
03

Thrombocytopenia — Platelets come from bone marrow megakaryocytes

Raw Material Not applicable here
Unlike haemoglobin — which depends on dietary iron, B12, and folate — platelets have no equivalent nutritional raw material. They are produced directly by megakaryocytes through cytoplasmic budding, a process that does not require an external precursor that can become deficient in the diet. The framework therefore applies as two categories only for platelets: Factory and Loss/Destruction. Recognising why a category is absent is as important as knowing the categories themselves.
Aplastic anaemia
Leukaemia
Chemotherapy
Key clue Pancytopenia — all cell lines affected, not just platelets.
Immune thrombocytopenic purpura (ITP)
Sepsis
Disseminated intravascular coagulation (DIC)
Key clues Isolated thrombocytopenia · Large platelets (marrow compensating) · No other cytopenias
Well child + low platelets → think ITP first.
04

Clotting Factor Deficiency — Clotting factors are proteins made in the liver

Haemophilia A (Factor VIII deficiency)
Haemophilia B (Factor IX deficiency)
Key clues Normal platelet count · Prolonged APTT · Normal PT · X-linked — males affected
Haemophilia is far more common in exams than rare Factor XIII deficiency. A young boy with haemarthrosis → think Haemophilia A first.
Chronic liver disease
Note The liver produces most clotting factors (I, II, V, VII, IX, X, XI). Liver failure = global coagulopathy. PT is the most sensitive early marker.
Disseminated intravascular coagulation (DIC)
Key clues in DIC Prolonged PT & APTT · Low fibrinogen · Thrombocytopenia · Elevated D-dimer · Schistocytes on blood film

Final Summary

When something is low — ask these three questions every time

① Raw Material?

  • Malnutrition → low albumin
  • Iron / B12 / Folate → anaemia
  • Haemophilia A/B → factor absence

② Factory Problem?

  • Liver disease → albumin, factors
  • Aplastic anaemia → pancytopenia
  • Leukaemia → bone marrow failure

③ Lost or Destroyed?

  • Nephrotic → albumin spilled in urine
  • Haemolysis / thalassaemia → RBCs
  • ITP / DIC → platelets & factors
RememberIs it not built?
RememberIs it not made?
RememberIs it being lost?
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