Serum Labs

Osteoarthritis lab findings

Normal labs; mild ↑ ESR/CRP in some cases. Synovial fluid: non-inflammatory (WBC < 2000/μL)

Rheumatoid Arthritis lab findings

↑ ESR, ↑ CRP; Positive RF; Positive anti-CCP antibodies; Mild normocytic anemia

Gout lab findings

↑ Serum uric acid; Synovial fluid: needle-shaped, negatively birefringent urate crystals

Osteoporosis lab findings

Normal labs (Ca²⁺, phosphate, ALP normal); DEXA: T-score ≤ -2.5

Osteomalacia/Rickets lab findings

↓ Vitamin D, ↓ Calcium, ↓ Phosphate; ↑ ALP, ↑ PTH

Paget's Disease of Bone lab findings

↑ ALP; Normal calcium and phosphate

Ewing Sarcoma lab findings

↑ LDH; Occasionally ↑ ESR; CBC: anemia may be present

Osteosarcoma lab findings

↑ ALP, ↑ LDH, ↑ ESR/CRP

Septic Arthritis lab findings

↑ WBC, ↑ ESR/CRP; Joint fluid: WBC > 50,000/μL, neutrophilic; Positive culture

Ankylosing Spondylitis lab findings

↑ ESR/CRP; HLA-B27+ in >90%; Mild normocytic anemia; RF & ANA negative

Achondroplasia lab findings

Normal labs; FGFR3 mutation; Imaging: characteristic skeletal changes

Osteoblastoma lab findings

Usually normal labs; Rare: ↑ ALP; Dx: imaging + biopsy

Giant Cell Tumor (GCT) of Bone lab findings

Normal labs; Rare: mild ↑ ALP; Dx: imaging + histology

Polymyalgia Rheumatica (PMR) lab findings

↑ ESR (often >40-100), ↑ CRP; Normocytic anemia; CK normal; ALT/AST may ↑; RF & ANA usually negative

Drug-Induced Myositis lab findings

↑ CK, ↑ Aldolase, ↑ AST/ALT; ↑ Myoglobin; ↑ K⁺/phosphate; Autoantibodies negative; TSH to check hypothyroidism

Myasthenia Gravis lab findings

Positive anti-ACh receptor or MuSK antibodies; CK normal

Lambert-Eaton Myasthenic Syndrome lab findings

Positive anti-VGCC antibodies; Normal or mildly ↑ CK

Polymyositis/Dermatomyositis lab findings

↑ CK, ↑ Aldolase, ↑ AST/ALT; Positive ANA, anti-Jo-1 (esp. polymyositis)

Rhabdomyolysis lab findings

↑↑ CK (>10,000), ↑ Myoglobin, ↑ Creatinine, ↑ K⁺/phosphate, ↓ Ca²⁺; Metabolic acidosis

Duchenne Muscular Dystrophy lab findings

Very ↑ CK (early stages); ↑ AST/ALT; Genetic test: dystrophin mutation

Myotonic Dystrophy lab findings

Mild ↑ CK; Genetic test: CTG or CCTG repeat expansion

Fibromyalgia lab findings

Normal labs; Possible ↑ substance P in CSF; Abnormal sleep studies

Chronic Fatigue Syndrome lab findings

Normal labs; May show mild cortisol/immune irregularities

Congenital Myopathies lab findings

Varies; mild ↑ CK; Confirm with genetic testing

Malignant Hyperthermia lab findings

↑ CK, ↑ K⁺/phosphate, Acidosis, ↑ Myoglobin; Genetic: RYR1/CACNA1S mutation

Botulism lab findings

CK normal; Diagnosis: clinical + stool/blood toxin assay

Tetanus lab findings

Normal labs; Clinical diagnosis

Poliomyelitis lab findings

↑ CSF WBC (lymphocytic); Dx: CSF PCR for poliovirus

Carpal Tunnel Syndrome lab findings

Normal labs; Dx: nerve conduction studies

ESR (Erythrocyte Sedimentation Rate)

Measures how quickly red blood cells settle at the bottom of a test tube. Faster = more inflammation. Nonspecific but helps detect inflammatory conditions.

CRP (C-Reactive Protein)

A protein made by the liver in response to inflammation. Rises faster than ESR and is more sensitive. High = inflammation, infection, or autoimmune disease.

RF (Rheumatoid Factor)

An antibody against the Fc portion of IgG. Found in rheumatoid arthritis and some infections.

Anti-CCP (Anti-Cyclic Citrullinated Peptide)

Highly specific autoantibody for rheumatoid arthritis. Helps confirm diagnosis.

ANA (Antinuclear Antibody)

Autoantibodies that target cell nuclei. Found in lupus, myositis, and other autoimmune diseases.

Anti-Jo-1

Autoantibody found in polymyositis and dermatomyositis, especially with lung involvement.

Anti-ACh Receptor / Anti-MuSK

Autoantibodies that attack the neuromuscular junction in myasthenia gravis.

Anti-VGCC

Autoantibodies against voltage-gated calcium channels in Lambert-Eaton syndrome.

CK (Creatine Kinase)

Enzyme found in muscle cells. Leaks into blood when muscles are damaged (rhabdomyolysis, myositis, DMD).

Aldolase

Another muscle enzyme that rises with muscle breakdown.

AST/ALT (Aspartate/Alanine Transaminase)

Liver enzymes that also rise when muscle cells break (not just liver damage).

Calcium (Ca²⁺)

Mineral crucial for bone, nerve, and muscle function. Low in osteomalacia, rhabdomyolysis.

Phosphate (PO₄³⁻)

Works with calcium for bones; rises in rhabdomyolysis, drops in vitamin D deficiency.

Potassium (K⁺)

Released when muscle cells die; high in rhabdomyolysis, can cause heart problems.

Creatinine

Waste product filtered by kidneys. High = kidney damage (e.g., from rhabdomyolysis).

Myoglobin

Muscle oxygen carrier; released in muscle injury, toxic to kidneys.

Substance P

Neurotransmitter involved in pain; elevated in CSF of fibromyalgia patients.

ALP (Alkaline Phosphatase)

Enzyme linked to bone formation and liver function. High in bone diseases like Paget's or bone tumors.

PTH (Parathyroid Hormone)

Regulates calcium and phosphate. Rises when calcium is low (e.g., vitamin D deficiency).

LDH (Lactate Dehydrogenase)

Enzyme found in almost all tissues. High in tumors (like Ewing sarcoma), inflammation, or tissue damage.

FGFR3 Mutation

Fibroblast growth factor receptor mutation; causes abnormal bone development in achondroplasia.

RYR1 / CACNA1S Mutation

Genes involved in calcium channels in muscle; mutations cause malignant hyperthermia.

Dystrophin Mutation

Gene defect in Duchenne Muscular Dystrophy. Dystrophin stabilizes muscle cells.

CTG/CCTG Repeats

Repeated genetic sequences in myotonic dystrophy; cause defective muscle function.

HLA-B27

Genetic marker linked to ankylosing spondylitis and related autoimmune conditions.

CSF WBC (Lymphocytic)

Found in viral CNS infections like poliomyelitis.

CSF PCR

Detects viral genetic material in the cerebrospinal fluid.

Stool/Blood Toxin Assay

Used to confirm botulism by finding toxins.

Nerve Conduction Studies

Measures electrical signals in nerves—used for carpal tunnel syndrome.