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Clin Lab Med Unit 2 > 3 ID And Body Fluids > Flashcards

3 ID And Body Fluids Flashcards

1
Q

Thin smear of material overlaid with crystal violent and rinsed, then safranin and rinsed again

A

Gram stain

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2
Q

Color for gram positive bacteria

A

Dark blue to purple

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3
Q

Color for gram negative bacteria

A

Pink/red

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4
Q

What’s an example of a gram variable organism?

A

Gardnerella vaginosis

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5
Q

Skin scraping, oral or vaginal secretions placed on a slide with a drop of KOH. The slide is heated briefly with a flame, then examined with a low power microscope

A

KOH prep

KOH dissolves host cells and bacteria, sparing FUNGI and elastin fibers

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6
Q

Slides prepared from lesion scrapings are stained with Giemsa or Wright stain preps. Presence of multinucleated giant cells indicates infection.

A

Tzank prep

Tests for Herpes virus

BUT IMMUNOFLUORESENCE MORE COMMONLY USED

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7
Q

A drop of centrifuged CSF is placed on a slide next to a drop of India ink. A cover slip is placed over the drops.

A

India ink, test for Crypotococci

Cryptococcosis are identified by LARGE CAPSULES which exclude the ink

India ink prep of the CSF will demonstrated round encapsulated yeast organisms consistent with Cryptococcus

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8
Q

Evaluation of bacteria too thin to absorb light from traditional microscopy are tested using…

A

Dark field microscopy (dark field illumination)

Useful in diagnosing Syphillis (T. pallidium) b/c it cannot be cultured and gram negative but too thin for staining

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9
Q

Visualization of ________ on dark field microscopy will reveal spirochetes

A

Syphillis (T. pallidum)

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10
Q

Additional testing for syphillis after dark field microscopy

A

Venereal Disease Research Laboratory (VDRL)
• CSF test - good for neuro syphillis
• Fluorescent treponema antibody absorption test (FTA-ABS)

Rapid Plasma Reagin (RPR)
• Serum test

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11
Q

What test should you use if worried about meningococcal meningitis?

A

Latex agglutination assay

Detects pathogen specific antibodies/antigens

CSF is tested for meningococcal capsular antigen

Also used for serum, saliva, or urine testing

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12
Q

What are ELISA tests and what’s the drawback?

A

Enzyme-linked immunoassay

Detects antibodies in serum

Takes up to 2 weeks for immune response, so may need repeat testing if tested too early

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13
Q

Primary test for ANA antibody

A

Indirect immunofluorescent assay (IFA)

Detects antibodies in serum or other body fluid

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14
Q

What is Nuclei Acid Amplification (NAAT)

A

Aka polymerase chain reaction (PCR)

Detects small quantities of bacterial/viral DNA/RNA sequences

Serum, CSF, and other body fluids can be tested

Results faster than ELISA

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15
Q

What is the acid fast bacilli (AFB) stain used for?

A

Specific for TB - sputum smear

Less sensitive than NAAT, but rapid and inexpensive

Mycobacterium culture most sensitive and specific for TB (for definitive Dx)

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16
Q

How is tuberculin skin testing performed?

A

Host cell-mediated immune response, delayed type hypersensitivity

Purified protein derivative (PPD) is injected intradermally, monitored for induration

(+) result means infection or exposure to TB, prior immunization with BCG

(-) can occur in positive patients who are immunocompromised

Individuals with patient contact, repeat at 8-10 weeks

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17
Q

Examples of non-sterile specimens

A

Pus taken off the skin/wound with a swab
Urine that is a “clean” catch
Sputum taken via expectoration
Throat swabs, genital swabs

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18
Q

Examples of sterile specimens

A

CSF, pleural, pericardial, peritoneal, or synovial fluids

All SHOULD be sterile

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19
Q

Inconsistent culture results can be due to…

A

Inadequate sample
Contaminated specimen
Wrong culture medium
Time delay from collection of sample to culture

Specimens should be brought promptly to the lab and plated promptly on the correct medium

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20
Q

What is the broth(tube) microdilution method?

A

For antimicrobial sensitivity testing

Bacteria is incubated in broth with dilutions of common antibiotics

Lowest concentration of abx that inhibits visible growth of bacteria is the MINIMUM INHIBITORY CONCENTRATION

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21
Q

What is the minimum inhibitory concentration (MIC)?

A

Minimum amount of abx you can use to treat patient

Pros:
MICs can be generated, tests standardized so reduced labor

Cons:
High cost compared to other methods
Miniature size of dilutions may result in less bacteria being analyzed

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22
Q

When comparing MICs, which antibiotic do you choose?

A

The one with the lowest MIC value, b/c it requires a small amount to inhibit bacterial growth

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23
Q

How does the agar dilution test work?

A

Each agar plate has a fixed concentration of an abx
Multiple plates with varying concentrations
Multiple samples are tested on a single set of plates

Pros:
MICs can be generated

Cons:
Reserved for resistant species
Species that require special growth conditions
Expensive, labor intensive

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24
Q

What is the Kirby-Bauer method?

A

Disk diffusion test
Bacteria grown on agar plate with filter paper disks containing a fixed concentration of abx
Growth inhibition around each of the abx is measured (can be susceptible, intermediate, or resistant)

Pros:
Inexpensive, simple

Cons:
Not recommended for fastidious or slow growing bacteria
No quantitative MIC

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25
Agar prepared with bacterial suspension, plastic strips imbedded with a graded concentration of antimicrobial is placed on the plate Growth inhibition along the strip is measured
Antimicrobial gradient method Pros: MICs obtained by identifying intersection of growth inhibition with gradient Standardized strips so less labor intensive Cons: Inaccuracy with some organisms
26
Considerations when selecting an antibiotic
Sensitivity reports - choose the lowest MIC if possible Can the abx get to the infected site Ex - will it cross the BBB in a CNS infection (may rule out use of the abx with the best MIC) Age of patient Current meds Comorbidities
27
Procedure for blood cultures
TWO different specimens, must be drawn for at least TWO different sites (NOT the IV) If one is positive and the other negative, the positive result is likely due to contaminant - BOTH must be positive
28
When should you draw the blood for culturing?
PRIOR to starting antibiotics Lab must be notified if abx were initiated prior to the blood draw
29
How long does it take for blood cultures to return?
Typically available in 24 hours, but 48-72 typical for ID of organism
30
Cases in which blood culture should be repeated within 48 hours of start of abx
Bacteremia due to S aureus (b/c worry for MRSA) Known/suspected endocarditis Infected site within area of limited antimicrobial penetration (abscess, joint space, CNS, abdomen) Persistent leukocytosis Prosthetic vascular grafts or cardiac pacemakers Pathogens known/suspected to be resistant to standard abx agents Unknown source for initial bacteremia
31
Aspiration of fluid from the pleural space
Thoracentesis
32
Aspiration of fluid from the pericardial sac
Pericardiocentesis
33
Aspiration of fluid from the abdominal cavity
Paracentesis
34
Aspiration of fluid from the spinal column
Lumbar puncture
35
Abnormal accumulation of fluid in any body cavity
Effusion
36
What are the two types of effusion?
Transudates Exudates Can occur in: Pleural space Peritoneal space Pericardial space
37
Accumulation of fluid in a body cavity due to filtration of blood serum across a physiologically intact vascular wall
Transudative effusion Due to pressure differences between body compartments
38
Transudative effusions are typically due to ...
Systemic disease Examples: CHF Hepatic cirrhosis Nephrotic syndrome Further Dx testing of fluid usually not needed
39
Accumulation of fluid within a body cavity due to inflammation and vascular wall damage
Exudative effusion - requires further testing to r/o cause ``` Examples of causes: Infection Malignancy Inflammatory disorder Trauma ```
40
Normal pleural fluid?
50 ml Should be clear, serous, light yellow RBCs: None WBCs: < 300/ml
41
The most common cause of exudative pleural effusions?
Parapneumonic effusion Usually secondary to: Bacterial pneumonia Lung abscess Bronchiectasis
42
Second most common cause of exudative pleural effusions
Malignancy 75% are caused by: Lung CA Breast CA Lymphoma
43
Non-infection, non-malignant exudative pleural effusions
Autoimmune disease Ex Lupus RA
44
RBCs in the pleural space is called
Hemothorax (usually following trauma) Fluid is serosanginous, with RBC >100,000 cells/uL Main causes: Trauma Malignancy Pulmonary Embolism
45
What’s special about PE and effusions?
PE may cause either a transudative or exudative effusion
46
Chylous effusions
Can occur in both pleural and peritoneal effusions Secondary to thoracic or abdominal lymphatic duct disruption or impairment Cloudy, milk effusion (+) triglycerides, lipids Causes: Trauma Malignancy to include lymphoma
47
Why do we perform thoracentesis?
Therapeutically to relieve pain/dyspnea To allow for better Radiographic imaging of the lung Diagnostically to establish if infectious, inflammatory, or malignant process
48
Why do we include the lateral decubitus view on CXR before thoracentesis?
Ensure the fluid is accessible by needle aspiration Check for fluidity Fluid will “layer” out with the patient in lateral decubitus position U/S helpful in localizing fluid, CT with contrast for more detail
49
Generally, a parapneumonic effusion should be sampled if it meets any of the following criteria:
It layers out >25mm on a lateral decubitus film It is loculated (pus—> adhesions) It is associated with thickened parietal pleura on CT (more indicative of malignancy) It is clearly delineated by U/s
50
Contraindications for thoracentesis
Use caution with significant thrombocytopenia
51
Potential complications of thoracentesis
``` Pneumothorax Intrapleural bleeding Hemoptysis Reflex bradycardia and hypotension Tumor seeding Empyema (collection of pus) Re-expansion pulmonary edema ```
52
What do we do to prevent re-expansion pulmonary edema?
Do not remove >1L via thoracentesis Do not perform thoracentesis bilaterally
53
Transudative vs Exudative Pleural Effusions: | Total protein levels
< 3 g/dL = Transudative > 3 g/dL = Exudative
54
Transudative vs Exudative Pleural Effusions: | Protein fluid/protein serum ratio
< 0.5 = Transudative > 0.5 = Exudative
55
Transudative vs Exudative Pleural Effusions: | Color/consistency
Clear thin fluid = transudative Cloudy, thick, viscous fluid = exudative
56
Transudative vs Exudative Pleural Effusions: | WBCs
< 300 cells/uL = transudative > 500 cells/uL = exudative
57
Transudative vs Exudative Pleural Effusions: | LDH fluid/LDH serum ratio
< 0.6 = transudative > 0.6 = exudative
58
What is LDH btw?
Marker for infection (from cellular breakdown and hemolysis)
59
Transudative vs Exudative Pleural Effusions: | Glucose (fluid:serum ratio)
Fluid and serum levels equal = Transudative Fluid glucose < serum glucose OR < 60 mg/dL = Exudative
60
Transudative vs Exudative Pleural Effusions: | pH
7.4-7.5 = transudative ≤ 7.3-7.4 = exudative
61
Transudative vs Exudative Pleural Effusions: | Amylase Fluid to Serum amylase
Equal = transudative Amylase fluid > amylase serum = exudative Amylase fluid will be elevated in pancreatic or esophageal injury
62
Pleural fluid analysis consists of ...
``` Gross appearance Cell count Gram stain Protein (serum and fluid) Glucose (serum and fluid) Amylase (serum and fluid) Cytology (looking for malignant cells) CEA (indicates bowel or breast CA in adults) Cultures (inc TB and fungal) ```
63
pH in pleural fluid < 7.3 usually indicates...
Infection, esophageal rupture, neoplasm
64
Elevation of amylase in pleural fluid usually indicates...
Pancreatitis, esophageal rupture, malignancy
65
Triglycerides or lipids in pleural fluid indicates...
Chylous effusion
66
Eosinophilia in pleural fluid indicates...
Parasitic infection, malignancy, TB
67
Light’s Criteria Rule for pleural fluid analysis
If at least one of the following three criteria is fulfilled, the fluid is defined as EXUDATE: 1) Pleural fluid protein/serum protein ratio > 0.5 2) Pleural fluid LDH/serum LDH ratio > 0.6 3) Pleural fluid LDH > 2/3rd ULN normal serum LDH
68
Describe normal peritoneal fluid
<50ml Clear, serous, light yellow RBCs: None WBCs: <300/uL
69
Accumulation of fluid within the peritoneal cavity is called...
Ascites
70
Common causes of ascites
``` Portal hypertension due to: Hepatic cirrhosis (81%) • 19% of patients with cirrhosis will have hemorrhagic ascites Alcoholic hepatitis Acute liver failure ``` Can also be caused by malignancy • 10% (most common of these is ovarian cancer)
71
Other unusual causes of ascites
``` Heart failure Infectious (TB or fungal) Hemodialysis-associated Pancreatic disease Nephrotic syndrome Severe malnutrition Myxedema (occurs with hyperthyroidism - severe widespread edema) ```
72
Gold standard for evaluating ascites
Abdominal U/s further evaluation for malignancy, consider CT or MRI
73
Indications for abdominal paracentesis
``` NEW ONSET ASCITES Or Preexisting ascites with: Fever Abdominal tenderness Mental status change Hypotension Peripheral leukocytosis Worsening renal function Trauma/severe cirrhosis (to r/o intra-abdominal bleed) ```
74
Potential contraindications for paracentesis
Coagulation abnormalities Patients with small amount of fluid Previous abdominal surgeries (b/c difficult to access peritoneal space with a lot of scar tissue)
75
Potential complications of paracentesis
Hypovolemia if large amount removed and fluid re-accumulates from intravascular volume Hepatic coma (patient with chronic liver disease) Peritonitis Tumor seeding with malignant ascites Organ perforation
76
Transudative vs Exudative Peritoneal Fluid: | Appearance
Clear, thin fluid = transudative Cloudy, thick, viscous = exudative
77
Transudative vs Exudative Peritoneal Fluid: | Glucose
Glucose equal to serum glucose = transudative Glucose < serum glucose or < 60 mg/dL = exudative
78
Transudative vs Exudative Peritoneal Fluid: | Protein
Total protein levels < 3g/dL or protein fluid/protein serum ratio < 0.5 = transudative Total protein levels > 3g/dL or protein fluid/protein serum ratio > 0.5 = exudative
79
Transudative vs Exudative Peritoneal Fluid: | WBCs
< 300 cells/uL = transudative > 500 cells/uL = exudative
80
Transudative vs Exudative Peritoneal Fluid: | LDH
LDH fluid/LDH serum ratio < 0.6 = transudative LDH fluid/LDH serum ratio > 0.6 = exudative
81
Transudative vs Exudative Peritoneal Fluid: | Serum to ascitic fluid albumin gradient (SAAG)
SAAG > 1.1 g/dL = transudative SAAG < 1.1 g/dL = exudative
82
SAAG classification for peritoneal fluid analysis
Serum-to-ascites albumin gradient Serum albumin MINUS ascitic fluid albumin = SAAG Transudative = gradient > 1.1 g/dL Most commonly caused by portal hypertension from hepatic cirrhosis Exudative = gradient < 1.1 g/dL THINK MALIGNANCY, infection, or inflammation
83
LDH fluid/LDH serum ratio > 0.6 can indicate...
Bowel perforation, malignancy, infection
84
Amylase elevation in peritoneal fluid can indicate
Pancreatic source, bowel perforation, malignancy, infection, esophageal rupture
85
Ammonia elevation in peritoneal fluid can indicate...
Ruptured or strangulated bowel
86
Bilirubin (brown effusion) in peritoneal fluid can indicate...
Bowel/biliary perforation
87
Urea/creatinine presence in peritoneal fluid indicates...
Possible bladder rupture (usually traumatic)
88
Presence of triglycerides in peritoneal fluid indicates...
Chylous effusion
89
Spontaneous bacterial peritonitis can occur in patients with...
Cirrhosis and ascites Often no obvious source of infection - likely originates in bowel Typical features: Abrupt onset of fever, chills, abdominal pain Rebound tenderness Labs will reflect exudative effusion Important to recognize and treat due to high mortality
90
What does pericardial fluid look like?
<50ml Clear, straw-colored NO RBCs NO WBCs***
91
When to suspect a pericardial effusion
In all cases of acute pericarditis Unexplained, new cardio metals on CXR w/o pulmonary congestion Unexplained persistent fever with no obvious source of infection Fever in patient with another disease process than can involve pericardium
92
Method of choice for evaluating pericardial effusions
ultrasound (echocardiography)
93
When NOT to do a pericardiocentesis
MOST OF THE TIME! If patient has an effusion, hemodynamically stable, and a source is known, can treat cause with serial f/u echos
94
When to consider a pericardiocentesis
Pericardial effusion with tamponade to relieve intrapericardial pressure if diastolic filling is inhibited Indicated if fluid is needed for Dx or if Dx might change management (ie malignancy)
95
Contraindications for pericardiocentesis
Caution with coagulopathy | Uncooperative patients
96
Complications of pericardial effusions
``` Laceration of coronary artery or puncture of myocardium Dysrhythmias MI Pneumothorax Vasovagal hypotension Pleural or pericardial infection ```
97
Why don’t we need to do analysis of protein, LDH, glucose, RBC or WBC for pericardial effusions?
Do not reliably differentiate an exudate from a transudative in a pericardial effusion and not helpful in establishing a Dx
98
Normal CSF
Normally 150-200ml circulating in spine and around brain Fluid clear and thin BBB allows only lipid-soluble, very small molecules to pass
99
What is the classic triad for meningitis?
Altered mental status (78%) Nuchal rigidity (88%) Fever (95%) Often rapid onset, patient quite ill Requires rapid assessment and treatment High risk of mortality and long term morbidity
100
Gold standard for diagnosing meningitis
CSF culture
101
Indications for Lumbar Puncture
Infection: Meningitis Encephalitis/abscess Neuro syphillis Malignant process: Brain tumor Spinal cord neoplasms MS Cerebral/subarachnoid hemorrhage
102
Contraindications for LP
Patients with increased intracranial pressure Severe vertebral degenerative joint disease Infection near LP site Patients taking anticoagulants
103
Complications of LP
``` CSF leak, headache Meningitis Herniation of the brain Spinal cord puncture Puncture of aorta or vena cava (retroperitoneal hemorrhage) Back pain, parasthesia in legs ```
104
When to do a CT before LP
Immunocompromised state Hx of CNS disease (mass, lesion, stroke, or focal infection) New onset seizure (within one week of presentation) Papilledema ALOC Focal neurological deficit
105
What to do before an LP
Two separate blood cultures should be drawn immediately if CNS infection is a concern Start empiric abx (remember, these must be able to cross BBB) Consider CT of head prior to LP based on IDSA guidelines) ABX should NOT be delayed pending CT scan
106
What should CSF look like?
``` Clear, colorless Pressure <20cm H2O RBCs (adult) 0-5cells/uL WBCs (adult) 0-5 cells/uL Protein: 15-45mg/dL Glucose: 50-75 mg/dL (approx 2/3 serum glucose) LDH < 40 units/L ```
107
Cloudy CSF indicates...
Infection, elevated protein
108
Pink/red CSF indicates
Bleeding from procedure or subarachnoid bleeding
109
Yellow CSF indicates
Xanthochromia (lysis of RBCs)
110
Decreased pressure with LP indicates
Hypovolemia (dehydration, shock), chronic CSF leak, nasal fracture with dural tear
111
Increased pressure with LP indicates...
Infection, intra-cranial bleeding, tumor, hydrocephalus
112
Large differences in opening/closing pressures with LP indicates...
Spinal cord obstruction (tumor), screaming/breath holding baby or child that then relaxes
113
WBCs > ______ is abnormal in CSF
> 5 cells/uL
114
Neutrophils in CSF
Bacterial/tubercular meningitis Cerebral abscess Subarachnoid bleeding Tumor
115
Lymphocytes in CSF
Viral, tubercular, fungal, syphillitic meningitis Multiple sclerosis Guillain-Barré syndrome
116
Eosinophils in CSF
Parasitic meningitis | Allergic reaction to radiopaque dyes
117
Macrophages in CSF
Tubercular, fungal meningitis Hemorrhage Brain infarction
118
RBCs > _____ is abnormal in CSF
>5 cells/uL
119
DDx of RBCs in CSF
``` Traumatic tap: • Normal CSF pressure • Bleeding decreases as CSF is withdrawn • No blood with repeat LP • Clotting present • Centrifuge —> clear fluid ``` ``` Subarachnoid bleed • Increased CSF pressure • Bleeding consistent throughout draw • Blood on repeat LP • No clotting • Centrifuge —> Xanthrochromia ```
120
_________ is present in >90% of patients within 12 hours of subarachnoid hemorrhage onset
Xanthochromia Hemoglobin —> oxyhemoglobin —> methemoglobin —> bilirubin (yellow) Can also be present in infections/inflammatory processes
121
Protein in CSF increases with...
Infectious/inflammatory processes, meningitis, encephalitis, myelitis May increase with bleeding/hemolysis Increased protein can indicate autoimmune disease
122
(+) oligoclonal gamma globulin bands
Multiple Sclerosis
123
CSF glucose < 2/3 serum glucose is indicative of
Meningitis | Neoplasm
124
Lactate dehydrogenase in CSF
Increased in bacterial meningitis/malignancy/intracranial hemorrhage
125
Lactic acid in CSF
Increased in bacterial/fungal meningitis BUT NOT VIRAL
126
Glutamine in CSF
Elevated in hepatic encephalopathy or coma
127
C-reactive protein (CRP) in CSF
Increased in bacterial meningitis
128
What stain do you use on CSF if suspecting toxoplasmosis?
Gemma’s/wright stain
129
Where do the four tubes collected during LP go?
Tube 1 —> chemistry/immunology analysis Tube 2 —> microbiology Tube 3 —> hematology Tube 4 —> hold

Clin Lab Med Unit 2 (4 decks)

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