Sensitivity, Specificity, PPV & NPV One Shot | Screening Test Properties | PSM Epidemiology

"Confused by Sensitivity vs Specificity? In this PSM (Community Medicine) lecture, Dr. Priyanka Sachdev simplifies the 2x2 Table, calculating PPV/NPV, and explains how to solve Screening Test Numericals for NEET PG & MBBS." Do “sensitivity” and “PPV” blur together in your head? In 25 crisp minutes, we’ll decode every screening metric with a single 2×2 table—so you nail MCQs, viva, and case stems without confusion. What you’ll learn ✅ 2×2 Table Setup (TP, FP, FN, TN): The backbone for every formula Core Metrics (with shortcuts): Sensitivity = TP/(TP+FN) → “Rule-out” (SnNout) Specificity = TN/(TN+FP) → “Rule-in” (SpPin) PPV = TP/(TP+FP), NPV = TN/(TN+FN) Accuracy = (TP+TN)/Total Likelihood Ratios (exam favorites): LR+ = Sens / (1–Spec) → “How much a positive rules in” LR– = (1–Sens) / Spec → “How much a negative rules out” Cut-off logic & trade-offs: Move cut-off left → Sens↑ Spec↓ | Move right → Spec↑ Sens↓ Validity vs Reliability: Validity (accuracy) = measures truth; Reliability (precision) = repeatability Inter- vs intra-observer variation, Kappa statistic basics Composite indices: Youden’s Index = Sens + Spec – 1, ROC curve & AUC interpretation Prevalence effect: Prevalence ↑ → PPV↑, NPV↓ (and vice-versa) Biases in screening: Lead-time, length, overdiagnosis—how they fool results Rapid MCQ hacks: “Test improves sensitivity—what happens to FP/FN?”, “Which metric changes with prevalence?” One-page exam diagram: 2×2 table + arrows for quick recall (we redraw it live) 3rd Prof Buster 1.0 (ENT • Ophthal • PSM • FMT): 4-month LIVE plan + 1-year recordings, color-coded notes, MCQ drills, viva boosters. Pair it with 2nd Prof Buster 2.0 for integrated revision momentum. 👉 Enroll now on the MedLive App to unlock: Structured timetable, live doubt-clears, and synced notes PYQ banks, topic tests, and rapid-revision PDFs Combo plans & bonuses for serious rankers 📲 Search “MedLive by Dr Priyanka” on Play Store & App Store. Pre-booking open—secure your seat today. #PSM #Epidemiology #CommunityMedicine #DrPriyankaSachdev #NEETPG #MBBS #Biostatistics #MedLive