Page 903 - Clinical Small Animal Internal Medicine

79 Laboratory Diagnosis of Infectious Diseases 841

Table 79.2 Collection, processing, and transport recommendations for different diagnostic tests in small animal infectious diseases.
VetBooks.ir Diagnostic test Specimen type Collection and processing Shipment
Follow all governmental guidelines relevant to a given infectious disease agent and clinical specimen

Histology Any tissue Samples collected for histology should never Double bag and leak‐proof container with
specimen be >1 cm thick (preferably 5–7 mm thick). adequate fixative
Fix in 10% buffered formalin (10× volume)
Cytology Any tissue Air‐dried smear should be prepared Blood or cytologic smears should never be
specimen or immediately after the sample has been collected mailed to the laboratory in the same package
fluid analysis to minimize cell deterioration. Alcohol fixation with formalin‐fixed tissues because formalin
is not needed. Analysis of various effusions and vapors will produce artifacts in the specimen.
fluids usually includes determination of protein Cytologic preparation should be transported at
content, total cell concentration, and cytologic room temperature in a plastic container. Fluid
examination. A sample of effusion/fluid should samples should be shipped chilled but not
be collected into an EDTA tube for routine frozen
analysis. A second sample should be collected
into a serum tube if any biochemical analyses
are to be performed or if a bacterial culture is
desired
Antibody or Blood, plasma, Serology generally requires serum, but Specimens can be refrigerated for up to a week
antigen testing serum, plasma is often satisfactory. For serum prior to shipment to the laboratory. Specimens
cerebrospinal samples, the blood should be drawn into a should be frozen at −20 °C or −80 °C if stored
fluid, urine plain tube or a separator tube. The sample for a longer period. Specimens can be stored
samples or should be held at room temperature for frozen for years without loss of antibody levels.
feces 20–30 min to allow complete clot formation For specimens collected for assays for antigen
and retraction. The sample should then be detection, results may be more susceptible to
centrifuged at high speed (~1000 g) for 10 variation with long specimen storage. The
min. In some instances, paired samples may laboratory should be contacted in order to
be required for an adequate diagnosis determine specimen storage and handling
requirements
Molecular Any specimen Collect aseptically to prevent contamination. For DNA analysis: submit specimens held at
testing For blood or bone marrow and DNA room temperature within 24 h of collection.
analysis, use preferably EDTA or acid citrate Specimens can be stored at 2–8 °C for 72 h, or
dextrose (ACD) anticoagulant at −20 °C or ≤−70 °C for prolonged storage.
For RNA analysis: use stabilization solution or
send immediately to the laboratory on wet ice.
For storage, freeze specimens at or below −70 °C
Isolation‐ Any specimen Collect aseptically to prevent contamination. Normally, specimens should be refrigerated and
culture Some agents might have special not frozen and delivered directly to the
requirements such as anaerobic culture or laboratory within 24 h
special media. Culture from blood should be
collected in special media bottles designed
to prevent coagulation and neutralize
antibiotic residues if animal was treated

on physical examination. Blood‐borne organisms such pod‐borne pathogens. Methods include the indirect fluo-
as Babesia (Figure 79.2) can be found in blood smears, rescent antibody (IFA) test, the enzyme‐linked
concentrated and stained buffy coat or splenic specimens. immunosorbent assay (ELISA), immunochromato-
Other important tissue samples used for the detection of graphic rapid in‐house devices, direct agglutination
these pathogens are lymph node aspirates, skin touch assays, and western blotting. The most common serologic
impressions, bone marrow, joint fluid, cerebrospinal tests employed in clinical practice are quantitative assays
fluid (CSF) or other body fluids and tissues. (IFA and ELISA) and qualitative tests (rapid in‐house
devices). In general, most of these methods have good
sensitivities and specificities but sensitivity and specificity
Serologic Testing (Antibody and Antigen greatly depend on the antigens employed. Whole‐para-
Detection)
site extracts are sensitive for the detection of subclinical
Antibody Detection or clinical canine and feline infections but provide lower
Several serologic methods can be used to detect specific specificity. On the other hand, assays that employ recom-
serum antibodies directed against protozoal and arthro- binant protein antigens are very specific but may lack