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The Basic Pain Laboratory Battery. CBCAcute phase proteins: ESR, CRPBlood Chemistry: Glucose, NA, K, CL, HCO3, CA, BUN, Crt, Uric acid, total protein, albumin, globulin, bilirubinEnzymes: Alkaline phosphatase, CK, LDH, AST, ALTThyroid: TSH, Free T4Vitamin B12 Labs depend on the clinical sit
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1. Use of Laboratory Tests in the Evaluation of Pain Alfredo Romero, MD
2. The Basic Pain Laboratory Battery CBC
Acute phase proteins: ESR, CRP
Blood Chemistry: Glucose, NA, K, CL, HCO3, CA, BUN, Crt, Uric acid, total protein, albumin, globulin, bilirubin
Enzymes: Alkaline phosphatase, CK, LDH, AST, ALT
Thyroid: TSH, Free T4
Vitamin B12
Labs depend on the clinical situation.
3. Complete Blood Count RBC: Anemia Hgb <13g/dL for men, <11d/dL women.
?Reticulocyte count: Index of bone marrow activity.
Elevated in Hemolytic anemia. Normal: 0.5-2.5%
?HbS: Heterezygous state’ sickle trait (SA). Pt asymptomatic. Homozygous state, sickle cell disease . Screening tests does not distinguish between SSD and SA. Definitive Diagnosis require Hgb electrophoresis.
WBC: Bacterial infection: leucocytosis with increased percentage of neutrophils and bands, but overwhelming infection in debilitated, elderly patients may fail to show leucocytosis.
?Drug-induced agranulocytosis: WBC < 4000may be caused by dilantin, carbamazepine, and NSAIDS.
Platelets: Severe thrombocytopenia <50.000, Thrombocytosis >900.000. Drug-induce thrombocytopenia: heparin, furosemide, cimetidine, quinine.
4. Electrolytes
Na: Hyponatremia: Symptoms such as nausea, malaise, lethargy, psychosis, seizures generally occur with Na < 120 mEq/L. Check diuretics, but also could caused by carbamazepine.
K: Hyperkalemia usually associated with renal failure, but drugs like B-blocker, potassium-sparing diuretics, NSAIDS, and cyclosporine could cause it.
5. Common Connective Tissues Diseases and Vasculitis Connective Tissue Diseases
Systemic lupus erythematosus (SLE)
Mixed connective tissue disease
Primary Sjogren’syndrome
Rheumatoid arthritis
Progressive systemic sclerosis (scleroderma)
Polymyositis and dermatomyositis
Vasculitis
Polyarteritis nodosa
Wegener’ granulomatosis
Temporal arteritis
Behcet’s disease
6. Connective Tissue Diseases SLE: ANA is the most sensitive test. Titers above 1:80 are considered positive, but a positive result is not sufficient for diagnosis. ANA titers can be seen in multiple conditions like hepatitis, malaria, other connective tissue disorders and thyroid disease.
RA: The most important rheumatoid factor is an IgM macroglobulin. Sensitivity of RF is 70% to 90%. Also can be seen in others conditions like SLE, scleroderma, dermatomyositis, hepatitis.
7. Serologic Testing for Collagen Vascular disorders Rheumatoid Factor: 80% sensitivity in RA
ANA: titer >1:320 have 95% specificity for SLE
ANCA: 90% positive in Wegener’s granulomatosis
Anti-Ro antibodies: 70% positive in Sjogren’s syndrome
Antinuclear (nuclear RNA): 60%-90% positive in scleroderma
Anti-SM: Highly specific for SLE
Anti-centromere: Suggest CREST
8. Thyroid Tests
Thyroid dysfunction may be confused with dementia
First check TSH
If THS is normal no further test is necessary
If TSH is abnormal check fee thyroxine (T4)
9. Prostatic Specific Antigen (PSA) Can detect prostate cancer 3 to 5 years before clinical symptoms appear
PSA is very specific for prostate disease, but no necessarily for prostate cancer
Can be positive in BPH, acute bacterial prostatitis, after cystoscopy, and even use of exercise bicycles.
10. Human Immunodeficiency Virus Patient may present with abdominal pain, painful neuropathies, oral cavity pain, headache, reactive arthritis, and post herpetic neuralgia.
Seroconversion generally occurs 6 to 10 weeks after infective exposure
Enzyme immunoassay testing for initial screening. Confirmatory test is Western Blot
Therapy goal is to keep viral load >10.000
Generally patient is asymptomatic with CD4 level above 500
11. Spirochetal Diseases Two “great imitators”
Syphilis: Caused by Treponema pallidum.
?Initial screening with non-treponemal test: VDRL and rapid plasma reagin (RPR).
?Confirmatory test : specific treponemal test. FTA-ABS
Lyme Disease: Caused by Borrelia burgdorferi which infects Ixodes dammini ticks.
?Laboratory evaluation is appropriate for patients with characteristic arthritic, neurologic, or cardiac symptoms
?Positive ELISA test should be confirmed by a Western blot.
12. Neuropathy
Diabetes and alcoholism are the most common cause of peripheral neuropathy in USA.
Other causes are amyloidosis, AIDS, PN, SLE, malignancy, myeloma, arsenium, lead, Vit B12 deficiency.
Level of Vit B12 < 200ng/L are abnormal. Look for elevated serum gastrin, intrinsic factor-antibody blocking antibodies. Shilling’s test may be necessary
13. Neuropathy Paraneoplastic neuropathy should be suspected in middle-aged patient, heavy smoker, c/o tingling and painful numbness all over. One indicator is serum antineuronal nuclear antibodies type I (ANNA:anti-HU).
Urine level .25 mg/d of arsenium are abnormal unless seafood was eaten recently
Lead neuropathy present with anemia, urine lead level >0.2mg/L. Blood lead levels can be misleading
14. Uric acid
Hyperuricemia is defined by a serum uric acid concentration >7mg/dL.
10% of gout patients may have normal levels
Many patients with hyperuricemia never experience a gout attack
Diagnosis is made with demonstration of uric acid crystals in the synovial fluid of an acutely inflamed joint
15. Liver Function Tests Only serum albumin, bilirubin, and PT provide useful information on how efficiently the liver is actually working
Normal LFT do not ensure a normal liver
The most common marker of hepatic injury are aspartate aminotransferase (AST) and alanine amonotransferase (ALT). Slight elevations of these enzymes may not indicate liver disease.
AST and ALT are found in skeletal muscle as well.
Alkaline phosphate (ALP) and gamma-glutamyltransferase are elevated with intra or extra-hepatic cholestasis
Serum ALP also originates from bone.
Serum conjugated bilirubin does not become elevated until liver has lost half of its excretory capacity.
Ammonia concentrations correlate poorly with the degree of confusion
16. Therapeutic Drug Monitoring and Testing for Drugs of Abuse Medications such as phenobarbital, valproic acid, carbamazepine, phenytoin, lithium carbonate, and triclyclic antidepressants have readily available assays.
Particularly in elderly patients, toxicity may occur at level normally considered therapeutic
Urine can be positive for cannabinoids several days after a single use of marijuana
Cocaine may be detectable for several weeks after cessation in heavy users
A positive result for amphetamines in the urine implies use within the last 24 to 48 hours.
17. Magnetic Resonance Technology Depicts anatomic sections in tomographic slides of varying thickness
It is based on the effects that a large magnetic field and radiofrequency (RF) pulses have on the nuclei of hydrogen atoms in body tissues.
Hydrogen nuclei can be made to align in large magnetic fields.
This alignment is perturbed with radiopulses.
When this RF is terminated, the nucleus attempt to realign giving off energy that can be detected.
The time it takes for the voltage to decay is expressed by two times constant the T1 and T2
18. Advantages of MRI Has no known adverse biologic effects
MRI does not use ionizing radiation
Produces substantially greater tissue contrast resolution
Provides significantly more information than CT about tissue characteristics
Beam-hardening artifacts seen with CT(e.g posterior fossa) do not occur with MRI
MRI has multiplanar capability
Define subacute an chronic collections of blood
MRI does not use iodinated contrast material (can be used in patients allergic to iodine).
19. Indications and Contraindications Indications: MRI is the imaging of choice for the evaluation of nearly all abnormalities involving brain, spine and musculoskeletal system (outstanding modality for evaluating various joints)
Contraindications: Cardiac pacemaker, ferromagnetic cerebral aneurysm clips, metallic foreign body near the eye, and cochlear implants
Limitations: Inability to demonstrate exquisite bone detail and calcification, long imaging times, limited availability in certain areas, expense study, and some patients experience claustrophobia.
20. Radionuclide Scanning Scintigraphy detects the distribution in the body of a radioactive agent injected into a vein
The strength of this test resides in its ability to portray the functional status of an organ or body part
The radioactivity is detected from outside the body with special gamma cameras
Localized defects that cause either too much or too little radioactivity to be emitted from a usually homogeneous area are then detected as pathologic lesions
21. Bone Scanning Technetium Tc 99m is an ideal isotope for bone scanning
Bone scan is a map of osteoblastic activity
Areas of increased or decreased bone turnover or remodeling can be identified
It is commonly use to detect metastatic disease, stress or fatigue fracture, , early detection of acute osteomyelitis or reactivation of the chronic form
22. Others Radionuclide Scanning Tests
Thallium myocardial imaging: For CAD
Ventilation-Perfusion scanning: (V/Q scan) for Pulmonary embolism
Iodine 125-labeled fibrinogen scanning: The most sensitive noninvasive test to detect early calf DVT.
23. Ultrasonography The ultrasound transducer converts electrical energy to high-frequency sound energy that is transmitted into the patient’s tissue.
The transmitted pulse encounters tissue interfaces that reflect a portion of the ultrasound beam back to the transducer.
US is severely limited by bone and by structures, such as bowel and lung, that contain gas.
US is very useful in evaluating liver, gallbladder, kidney, ureteres, urinary bladder, pancreas, pelvic organs, thyroid, and cystic masses of the extremities
Doppler US is 84% sensitive in detecting DVT above the knee.
24. Contrast-Enhanced Examinations Arthrography: Imaging after injection of contrast material into a joint space.
Effective in demonstrating rotator cuff injuries, adhesive capsulitis, ligamentous injuries. MRI has replaced arthrography.
Myelography: Introduction of water-soluble, nonionic contrast agent into the subaracnoid space via lumbar puncture.
This procedure is effective and accurate for demonstrating the subarachnoid space, spinal cord, and nerve roots.
Almost replaced by MRI
27. Selection of Radiologic Imaging Headache and Orofacial pain
?Acute, severe headache are best imaged by CT
?For subacute or chronic headaches MRI is the procedure of choice.
?Orofacial pain may require dental radiography, temporomandibular pain at require MRI or arthrography. Sinusitis is best evaluated by CT
Thorax and Abdomen
?Investigated with CT, US, and contrast studies
Neck and Upper Extremities
?Investigated with routine radiography and or MRI
28. Selection of Radiologic Imaging Low Back and Lower Extremity
?MRI is the procedure of choice for screening patients
with low back pain
?In asymptomatic adults 30% are found to have a
mayor abnormality on MRI.
?Generally a bulging disc is not associated with
sciatica, whereas protruded disc is.
CT myelography, is often the best and definitive diagnostic modality for arachnoiditis and epidural fibrosis.