Interpretation and Application of Common Lab Work

Purpose of Lab Tests

• screening

• diagnosis

• monitoring

• modification of therapy program according to laboratory findings

screening

used to screen for occult disease

diagnosis

used as a supplement to physical signs/symptoms, thus aiding diagnosis

monitoring

used to follow the course of a disease or conditions; look at trends

Parkinson’s Disease

a neurodegenerative disease characterized by a loss of dopaminergic neuron function resulting in bradykinesia, rigidity, tremors, & postural instability

MS Changes

• CT Scan head: no acute abnormality

• medications unchanged

• complete blood count (CBC): WBCs 12K, N 79%)

• urinalysis (UA): 20-30 WBCs, nitrite + LE + (leukocyte esterase), many bacteria; C/S pending

• basic metabolic panel (BMP): normal

• Dx?

Complete Blood Count (CBC)

Common Indications:

• infections - look at WBC(white blood cells) & individual sub-types of white cells

• bleeding, bruising, petechiae - look at hemoglobin (Hgb), platelets

Trends: more important than one point in time

• is the white blood cell count or hemoglobin trending up or down over the clinical course?

take into context the past medical hx or surgical history

• is there a history of cancer, recent surgery, medication (blood thinners, steroids, chemo), cardiac, or pulmonary problems

CBC Format

Hemoglobin (Hgb)

• iron metalloprotein in RBCs responsible for binding oxygen; 1RBC has approx 280K Hgb molecules

• measures the amount of Hgb in the body

  • low Hgb = anemia

  • high Hgb = polycythemia

• Normal female: 12-16g/dL Normal male: 14-17g/dL

• critical cut-off level is <8g/dL

  • case by case basis

  • essential ADLs may be permitted (as per Acute Care section-APTA)

• pulse oximeter

pulse oximeter

reflects % O2 saturation; not necessarily a reflection of Hgb levels

Hematocrit (Hct)

• proportion of blood volume that is occupied by RBCs; assists in evaluating hydration status, anemia or polycythemia

• norma female: 36-47% Normal male: 41-51%

• increased in polycythemia, high altitudes, heavy smoking, chronic lung disease, congenital heart defects

• decreased in anemia and hemodiltion

• critical cut-off level is <25%

  • case by case basis

  • may participate in essential ADLs with assistance

Red Blood Cells

Low levels = anemia (different types)

• acute blood loss-normocytic (normal size)

• slow blood loss (Fe deficiency) or chronic disease-microcytic (small)

• Vitamin B12 or folate deficiency-macrocytic (big)

High levels = polycythemia

• polycythemia vera

• secondary polycythemia

• vigorous exercise

• high altitude

• smoking

MCV (mean corpuscular volume) - Size of RBC; helpful in determining anemia type

Platelets

• tiny cellular fragments that form clots; stop or prevent bleeding

• normal value is 150,000-350,000/uL

• thrombocytopenia (low levels) lead to poor clotting; easily bruised or bleeds

• thrombocytosis (high levels) occur during infection inflammatory processes, neoplasm

• Acute Care Section APTA Guidelines:

  • <10,000 &/or temp >100.5 = bed rest

  • 10,000-20,000 = therapeutic exercise/bike (no resist)

  • >20,000 = therapeutic exercise/bike

WBC Types

• indicates the functional status of the immune system

• neutrophils 60-70% increased in infection

• Eosinophils 1-4% remember NAACP

• Basophils 0.5-1% leukemias, certain drugs

• lymphocytes 20-40% increased in viral infections inflammation

• monocytes 4-8% increased in viral, bacterial and/or parasitic infection

WBC - Neutrophils

• normal values 60-70%

• primary infection fighters; first line of defense

• left shift (proliferation of immature cells from the bone marrow-normal response)

  • acute infection or inflammation

  • certain medications

• right shift (proliferation of mature cells)

WBC-Lymphocytes

• normal 20-40%

• often increased in chronic inflammation

• important cells that determine the “type” of response the immune system mounts

  • natural killer T cells attack body cells that have become cancerous or taken over by viruses

  • B cells make antibodies that attack bacterial cells and toxins

WBC - Eosinophils

• normal 1-4%

• elevated in hay fever, asthma, dermatomyositis, parasitic infections, neoplasm

• remember → NAACP

  • Neoplasms

  • Addison’s Disease (disease of the adrenal gland)

Urinalysis

• for suspected renal disease, urinary tract infection (UTI), diabetes (DM), cancer

• Protein: normally very little

• pH: normally 6-7 (1-3 acidic = gout)

• Glucose: normally none in urine, if detected indicates DM, gestational diabetes, pancreatic or other endocrine disorders

• WBC: normal is <10/hpf; indicates inflammation or infection

• Nitrite: E.Coli makes an enzyme that ionizes normal urine nitrates to nitrites

• Leukocyte esterase (LE): enzyme released by WBC in the urine; indicator of infection

• a urine culture is the gold standard for diagnosis of a UTI

Diagnosis

• urinary tract infection - treated with antibiotics

• implications for physical therapy - resume rehab after mental status returns to baseline for this patient; may still be on antibiotics, but should not be febrile

Complete or Basic Metabolic Panel (CMP or BMP)

Indications:

• electrolytes (Na+, K+, CO2, Cl-)

• renal function (BUN, Cr)

• liver function (ALT, AST)

• Protein levels (albumin)

• Glucose

Na+

• sodium

• normal values between 135-145 mEq/L

• hypernatremia can result in confusion and/or lethargy

• hyponatremia can result in muscle cramps, confusion, lethargy, and/or nausea

K+

• potassium

• normal value between 3-5-5.0 mEq/L

• hyper/hypokalemia or abnormally high/low levels increase risk of cardiac arrhythmia

• review medications, check renal function

• PT contraindicated when 3.4>K+>5.1

Serum CO2

• bicardbonate

• normal value between 22-27 mEq/L

• abnormal levels indicate renal or pulmonary problems

• PT contraindicated when 10>CO2>40

Serum Glucose

• normal value between 70-130 mg/dL

• concern in diabetics — low/high levels can lead to mental status changes, seizures, fatigue, headache

• guidelines will vary from facility to facility

• consider the patient’s “trend”; treat the patient-not the paper!

• PT contraindicated when 60>glucose>300

Hemoglobin A1c (Let’s talk about diabetes)

• measures the amount of glycosylated hemoglobin (portion of Hgb that has glucose attached to it) over a 3-month span

• used to screen, diagnose, and monitor diabetes

• separate measurement from CMP/BMP panels

• given as a percentage

  • Hgb A1c <5.7% = normal level

  • Hgb A1c 5.7-6.4% = pre-diabetes

  • Hgb A1c 6.5-7.9% = diabetic patient

  • Hgb A1c >8% = poorly controlled diabetic

Coagulation Markers

Labs: measure TIME needed to clot

• PT: prothrombin time (12-15 secs)

• INR: international normalized ratio (0.8-1.2)

• PTT: partial thromboplastin time (25-35 secs)

Medications:

• Coumadin

• Heparin:

• Lovenox

• Eliquis

Therapy is contraindicated if prothrombin time is 2.5x greater than reference range - could result in spontaneous bleeding

coumadin

acts on extrinsic clotting factors; measured by PT and INR

Heparin

acts on intrinsic clotting factors; measured by PTT

Lovenox

injectable anticoagulant; does not require monitoring; peak effectiveness at 3-5 hours after administration

Eliquis

oral anticoagulant; does not require monitoring; peak effectiveness at 1.7 hrs after administration (many others)

Red Incision

• aspiration performed by the orthopedic provider reveals turbid, opaque fluid with > 10k WBC and low glucose

• ESR = 78, CRP = 3.6, WBC = 15k

• the surgeon schedules the patient for an I&D of the joint, IV antibiotics, and possible extraction of the hardware with revision anthroplasty

Red Incision Lab Values

• C-Reactive Protein (CRP = 3.6 (normal range 0.0-1.0mg/dL)

• erythrocyte sedimentation rate (ESR) = 78 (normal range 0-20 mm/hr)

joint fluid analysis

erythrocyte sedimentation rate (ESR)

• during inflammation, fibrinogen increases causing RBCs to stick together becoming heavy

• rate of settling of RBCs in anticoagulated blood measured in mm/hr

• marker of inflammation, infection, or neoplastic process

• indications infection or inflammatory conditions (RA, myopathy, not OA)

• high sensitivity, low specificity

C-Reactive Protein (CRP)

• also a marker of inflammation

• an acute phase protein produced by the liver

• elevated earlier than ESR in acute inflammation

  • 6-8 hrs inflammatory process

• can be used instead of/in conjunction with an ESR level

antinuclear antibody (ANA)

• screening test for autoimmune disease

• seen in systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), scleroderma, polymyositis, dermatomyositis

• absence rules out SLE

• found in 3-4% of the normal population

• normal titers: 1:20-1:40 blood volume to dilution agent; ANA still detectable

• higher titers (i.e. 1:160) necessitates further workup

Rheumatoid factor (RF)

• usually present in RA 75% of the time and occasionally in other connective tissue diseases

• Normal is <15 U/mL

• absent in early RA

• absent (RF-) in seronegative spondyloarthropathies (types of inflammatory diseases that affect the spine and nearby joints)

Thyroid Stimulating Hormone (TSH)

• is a peptide hormone synthesized & secreted by the anterior pituitary. It regulates secretion of thyroid hormones

• often overlooked cause of diffuse joint pain & myalgias

• usually affects shoulders & hips

• may experience swelling of knee joint & small joints of hands & feet similar to rheumatoid disease

• considered an autoimmune disease; women are more commonly affected than men with a 4-6:1 ratio

Human Leukocyte Antigen B27 (HLA-B27)

• HLAs are glycoproteins found on the surface of the leukocytes; used in cell communication

• can be found in up to 10% of the population

• present in seronegative spondyloarthopathies

• a spondyloarthopathy is any joint disease involving the vertebral column

seronegative

means rheumatoid factor is NOT present in the patient’s serum

Seronegative Spondyloarthropathies (HLA-B27 +, RF-, ANA-)

• ankylosing spondylitis (90%)

• reactive arthritis/formerly reiters syndrome (75%)

• psoriatric arthritis/arthritis of ulcerative colitis or Crohn’s

Creatine Kinase/Creatine Phosphokinas (CK or CPK)

• muscle enzyme present in sarcoplasm

• mechanism: injury or disease of skeletal (CK-MM) or cardiac muscle (CK-MB) releases it into blood stream

• Normal levels (24-194 IU/L)

• seen with MI, CVA, inflammatory myopathies, rhabomyolysis, trauma, post surgical, vigorous exercise; reaction to cholesterol-lowering drugs (statins)

Uric Acid

• elevated in purine-rich diet (organ meats, sardines, seafood), high fructose diet, alcohol

• 3.6 mg/dL to 8.3 mg/dL considered normal levels

• increased in gout, renal disease, dehydration, chemotherapy

• gout attacks can occur due to beer consumption, diuretics, trauma, obesity