PA22.3-5 | Laboratory Panel Interpretation — Summary & Reflection

REFLECT

Before you move to the summary, take two minutes to construct a single table in your notebook that lists all four panels (semen analysis, TFT, LFT, RFT) and, for each, names: (1) the two most important values you check first, (2) the one ratio that is most diagnostically powerful, and (3) the one pre-analytical error that could make you reach the wrong conclusion.

This exercise builds the rapid triage pattern that attending physicians use automatically. If you struggled to recall any entry, go back to that section before proceeding.

KEY TAKEAWAYS

Laboratory panel interpretation — key takeaways:

Semen analysis (WHO 2021):
- Six axes: volume, concentration, total motility, progressive motility, morphology, vitality
- Oligospermia (< 16 × 10⁶/mL), asthenospermia (total motility < 42%), teratospermia (morphology < 4%)
- OAT syndrome = combined defect; hypospermia + OAT suggests ejaculatory or anatomical factor
- Pre-analytical rule: 2–7 days abstinence; confirm azoospermia with two centrifuged samples

Thyroid function tests:
- Primary hypothyroidism: ↑↑ TSH + ↓ FT4 (+ anti-TPO for Hashimoto's)
- Primary hyperthyroidism: ↓ TSH + ↑ FT4/FT3
- Secondary hypothyroidism: low/normal TSH + ↓ FT4 — request if pituitary disease suspected
- Subclinical: TSH abnormal, T4 normal; anti-TPO guides treatment in subclinical hypothyroidism

Liver function tests:
- Three groups: hepatocellular (ALT/AST), cholestatic (ALP/GGT/bilirubin), synthetic (albumin/PT)
- AST:ALT > 2:1 → alcoholic liver disease; < 1 → viral/NAFLD
- Jaundice: prehepatic (unconjugated ↑, LFTs normal), hepatic (mixed, LFTs ↑), posthepatic (conjugated ↑, ALP/GGT ↑↑↑, dark urine, pale stools)
- PT/INR is the earliest marker of acute synthetic failure

Renal function tests:
- Urea:creatinine ratio > 100 (SI) → prerenal; 40–100 → intrinsic; < 40 → liver failure/malnutrition
- AKI vs CKD: bilateral small kidneys, anaemia, ↑ phosphate, ↑ PTH = CKD
- Prerenal vs ATN: urine Na⁺ < 20 vs > 40; FENa < 1% vs > 2%
- eGFR unreliable in acute settings — report raw creatinine trend