Interfering Substances; Expected Values - Siemens ADVIA 2120 Operator's Manual

♦ Incomplete sample aspiration on the ADVIA 120
♦ Incomplete incubation time
•
Samples with total protein content 500 – 1000 mg/dL should be analyzed
within 1 hour after preparation with CSF reagent. Increased protein
concentrations may cause precipitation of cells and proteins in the prepared
sample.
•
The ADVIA 120 CSF RBC count provides no information to distinguish
between elevated CSF RBC counts due to cerebral hemorrhage or traumatic
spinal tap.

Interfering Substances

•
Samples containing oily or fatty contaminants may interfere with the ADVIA
120 cell counts. Avoid oily contaminants, such as silicon used to lubricate
the stoppers of blood collection tubes.
•
RBC coincidence events in samples with RBC counts greater than 1500
cells/µL may cause falsely elevated CSF WBC counts and incorrect CSF
WBC differentials. Such a sample should be diluted to acceptable RBC limits
in PBS before preparation with CSF Reagent and reanalyzed.
•
RBCs in samples that have been diluted with normal saline before
preparation with CSF reagent require a longer incubation period to sphere the
RBCs in the sample. The preferred diluent for CSF samples is PBS. Samples
diluted with normal saline must be prepared with CSF reagent immediately
after dilution and must be incubated for 10 minutes in order to allow
complete RBC sphering.
•
Samples containing microcytic and/or hypochromic RBC populations may
falsely decrease the CSF RBC count.
•
Samples containing RBC populations that fail to sphere completely may give
falsely elevated CSF WBC counts and incorrect CSF WBC Differentials.
•
Budding yeast forms may overlay both CSF RBC and CSF WBC counting
areas, falsely elevating CSF RBC and WBC counts.

Expected Values

The range of expected values for the CSF Assay can vary depending on patient
age or other patient characteristics. It is recommended that each laboratory
establish its own range of expected values based on their patient population. The
following range of expected values is based on ADVIA 120 results from 52 CSF
specimens that were determined to be normal by manual methods.
Parameter
WBC (cells/μL)
9-40
aspiration on the ADVIA 120
Expected
Value
0-10
Regulatory Information