Question 1: Which one of the following biochemical abnormalities can be produced by repeated vomiting?
- A. Metabolic acidosis
- B. Metabolic alkalosis (Correct Answer)
- C. Ketosis
- D. Uraemia
Explanation: ***Metabolic alkalosis***
- Repeated vomiting leads to the loss of **hydrochloric acid (HCl)** from the stomach, causing **hypochloremic metabolic alkalosis** with an increase in serum **bicarbonate (HCO3-)** and a rise in blood pH.
- The loss of H+ and Cl- ions results in **compensatory hypokalemia** as the kidneys exchange K+ for H+ to maintain electroneutrality.
- **Volume depletion** from vomiting triggers aldosterone secretion, which further promotes K+ loss and H+ excretion, perpetuating the alkalosis (contraction alkalosis).
- This is one of the most common causes of metabolic alkalosis in clinical practice.
*Metabolic acidosis*
- This condition is characterized by a decrease in **serum pH** and **bicarbonate levels**, typically due to excess acid production or bicarbonate loss from diarrhea or renal tubular acidosis.
- Vomiting does not directly cause metabolic acidosis; rather, it leads to the opposite effect by removing acidic gastric contents.
*Ketosis*
- **Ketosis** occurs when the body metabolizes fat for energy, producing **ketone bodies**, common in conditions like uncontrolled diabetes or prolonged starvation.
- While severe, prolonged vomiting with reduced oral intake can indirectly lead to starvation ketosis, the primary and most characteristic biochemical abnormality of repeated vomiting is metabolic alkalosis, not ketosis.
*Uraemia*
- **Uraemia** is a syndrome caused by the accumulation of **nitrogenous waste products** (urea, creatinine) in the blood, primarily due to kidney failure.
- Vomiting may be a *symptom* of uraemia, but it does not *cause* uraemia. Kidney function is the primary determinant of urea levels.
Question 2: Biochemical screening of newborn infants by heel-prick blood samples is performed by using the
- A. Duchenne Card
- B. Guthrie Card (Correct Answer)
- C. Tay-Sachs Card
- D. Maple Card
Explanation: ***Guthrie Card***
- The **Guthrie card**, also known as a **newborn screening card** or **filter paper card**, is specifically designed for collecting **heel-prick blood samples** from newborn infants for biochemical screening.
- It allows for the detection of various **inborn errors of metabolism** and other genetic conditions, such as **phenylketonuria (PKU)** and **congenital hypothyroidism**.
*Duchenne Card*
- There is no specialized "Duchenne Card" used for **newborn biochemical screening**.
- **Duchenne muscular dystrophy** is a genetic disorder diagnosed through **genetic testing** or **muscle biopsy**, not typically a specific screening card at birth.
*Tay-Sachs Card*
- There is no specific "Tay-Sachs Card" used for routine **newborn biochemical screening**.
- **Tay-Sachs disease** is a **lysosomal storage disorder** diagnosed through enzyme activity tests or **genetic analysis**, often in populations at higher risk or with clinical suspicion.
*Maple Card*
- There is no recognized "Maple Card" for **newborn biochemical screening**.
- "Maple" could potentially refer to **Maple Syrup Urine Disease (MSUD)**, which is one of the conditions screened for using the **Guthrie card**, but there is no dedicated "Maple Card."