PANCE

These items test choosing the right study, its risks, specimen collection, and interpretation. Reference ranges capture the central 95% of healthy people, so interpret borderline values in context; ranges vary slightly by laboratory.

High-Yieldadultreferenceranges

Panel	TestandTypicalRange	InterpretationPearls
CBC	WBC 4 ,500–11 ,000/µL; Hgb M 13 .5–17 .5 F 12–16 ,	Leftshift(↑bands)=bacterialinfection;lymphocytosis=
	g/dL; Hct M 41–53% F 36–46%; MCV 80–100 fL; ,	viral; eosinophilia = parasites , allergy . MCV <80 microcytic
	platelets 150 ,000–400 ,000/µL	(irondeficiency thalassemia chronicdisease);>100 , ,
		macrocytic(B12 folate liverdisease) , ,
BMP	Na 136–145 mEq/L; K 3 .5–5 .0; Cl 98–106; HCO 22– 3	BUN:Cr >20:1 = prerenal . Hemolysis falsely ↑ K .
	28; BUN 7–20 mg/dL; Cr 0 .6–1 .3 mg/dL; fasting	Hypokalemia: U waves; hyperkalemia: peaked T → wide
	glucose 70–99 mg/dL; Ca 8 .5–10 .5 mg/dL	QRS Hypercalcemia:stones bones groans moans short . , , , ,
		QT;hypocalcemia:tetany longQT ,
Otherchemistry	Mg 1 .7–2 .2 mg/dL; phosphate 2 .5–4 .5 mg/dL;	Replete Mg to correct K Prediabetes: HbA1c 5 .7–6 .4% or .
	lactate <2 mmol/L; HbA1c <5 .7%; TSH ≈0 .4–4 .0	fasting glucose 100–125; diabetes ≥6 .5% or ≥126 (confirm)
	mIU/L
LFTs	AST≈10–40U/L;ALT≈7–56U/L;ALP≈44–147U/L;	ALT more liver-specific . AST:ALT >2:1 = alcohol; thousands
	total bilirubin 0 .1–1 .2 mg/dL (direct ≤0 .3); albumin	= viral , ischemic , acetaminophen . ↑ ALP + ↑ GGT =
	3 .5–5 .0 g/dL	cholestasis; normal GGT = bone . Indirect bilirubin:
		hemolysis Gilbert;direct:hepatocellularorobstruction ,
Coagulation	PT 11–13 .5 s; INR 0 .8–1 .1; aPTT 25–35 s; fibrinogen	PT/INR(extrinsic):warfarin vitaminKdeficiency liver , ,
	200–400mg/dL	disease aPTT(intrinsic):heparin hemophilia von . , ,
		Willebranddisease ↓fibrinogen:DIC .
ABG	pH 7 .35–7 .45; PaCO 35–45 mmHg; HCO 22–26 2 3	Primary disorder → compensation → anion gap
	mEq/L; PaO 80–100 mmHg 2
Urinalysis	Specific gravity 1 .005–1 .030; pH 4 .5–8; negative	Nitrite = gram-negative bacteriuria . RBC casts = GN; WBC
	protein glucose ketones blood leukocyte , , , ,	casts = pyelonephritis; muddy-brown casts = ATN; fatty
	esterase nitrite ,	casts = nephrotic . Heme-positive without RBCs =
		myoglobinorfreehemoglobin

Anion gap = Na − (Cl + HCO₃) normal ≈ 8–12

Winter formula: expected PaCO₂ = 1.5 × HCO₃ + 8 ± 2

Corrected Ca = measured Ca + 0.8 × (4.0 − albumin)

Albumin (half-life ~20 days) reflects chronic synthetic function; PT/INR is the acute marker. Troponin rises 3–4 hours after infarction, peaks at 12–24 hours, stays up 7–14 days. BNP rises with ventricular stretch (cardiac vs pulmonary dyspnea). D-dimer is sensitive but nonspecific — use it to exclude VTE only at low pretest probability. TSH is the best thyroid screen (add free T4).

Blood cultures: two sets from separate sites before antibiotics. Urine: midstream clean catch. ABG: radial artery after a modified Allen test.

Test Statistics: The Worked 2×2 Table

Sensitivity (true-positive rate): a negative sensitive test rules out (SnNout) — ideal for screening. Specificity (true- negative rate): a positive specific test rules in (SpPin). Predictive values change with prevalence — higher prevalence raises PPV and lowers NPV; likelihood ratios do not.

Example:Newtest,1,000Patients,Prevalence10%

	DiseasePresent	DiseaseAbsent	Total
Testpositive	TP=90	FP=180	270
Testnegative	FN=10	TN=720	730
Total	100	900	1000 ,

Sensitivity = TP / (TP + FN) = 90 / 100 = 90%

Specificity = TN / (TN + FP) = 720 / 900 = 80%

PPV = TP / (TP + FP) = 90 / 270 = 33%

NPV = TN / (TN + FN) = 720 / 730 = 98.6%

LR+ = sens / (1 − spec) = 0.90 / 0.20 = 4.5

LR− = (1 − sens) / spec = 0.10 / 0.80 = 0.125

Two of three positives are false because the disease is uncommon. LR+ >10 or LR− <0.1 is strongly conclusive.

Stroke rate: control 10%, treatment 6%

ARR = 10% − 6% = 4% (0.04)

RRR = ARR / control rate = 0.04 / 0.10 = 40%

NNT = 1 / ARR = 1 / 0.04 = 25 patients

NNH = 1 / absolute risk increase; round up to a whole patient.

Imaging Selection

Chest radiograph is PA and lateral; portable AP for unstable patients (magnifies the heart). CT uses radiation and iodinated contrast (caution with AKI; hold metformin if eGFR <30). MRI has superior soft-tissue contrast without radiation; screen for pacemakers and metal, and avoid gadolinium with eGFR <30 (nephrogenic systemic fibrosis). Ultrasound is radiation-free but limited by habitus and bowel gas. Nuclear studies: bone scan (metastases), V/Q, thyroid uptake, stress perfusion. An acute abdominal series shows free air and air-fluid levels.

ClinicalQuestion	StudyofChoice
Suspectedstrokeorsubarachnoid	NoncontrastCThead(LPifCTnegativeandSAHstillsuspected)
hemorrhage
Acutecholecystitis biliarycolic ,	RUQultrasound;HIDAscanifequivocal
Appendicitis	CTwithcontrast;ultrasoundfirstinchildrenandpregnancy
Nephrolithiasis	NoncontrastCT;ultrasoundinpregnancyandchildren
Pulmonaryembolism	CTpulmonaryangiography;V/Qscanifcontrastcontraindicated
Aorticdissection	CTangiography;TEEifunstable
AAAscreening;DVT Testicularorovariantorsion;ectopic pregnancy	Abdominalultrasound;compressionduplexultrasound Dopplerultrasound;transvaginalultrasoundwithquantitativehCG

Bestinitialimagingbyclinicalquestion(Continued)

ClinicalQuestion	StudyofChoice
Cordcompression caudaequina , ,	MRI
osteomyelitis occultscaphoidfracture ,
Pneumoperitoneum;bowelobstruction	Uprightchestradiograph;CTabdomen/pelvis

ECG Basics

Read rate, rhythm, axis, intervals, then ST–T changes. Rate = 300 ÷ large boxes between R waves. Axis is normal when QRS is upright in I and aVF. ST elevation = injury (II, III, aVF inferior/RCA; V1–V4 anterior/LAD; I, aVL, V5–V6 lateral/circumflex); ST depression = ischemia or reciprocal change.

SnNout, SpPin; prevalence changes PPV and NPV, not

INR reflects acute hepatic synthetic function; albumin

sensitivity or specificity.

reflects chronic.

NNT = 1 / ARR; LR+ = sens / (1 − spec).

Noncontrast CT for stroke and stones; RUQ ultrasound for gallbladder; CTA for PE and dissection.

BUN:Cr >20 prerenal; RBC casts GN; WBC casts pyelonephritis; muddy-brown casts ATN.

Upright in I and aVF = normal axis; PR 0.12–0.20 s, QRS <0.12 s.