IFA + Hgb Electrophoresis Flashcards
general principle of IFA
slide with substrate (HEP-2 or MSK) + pt sample with Ab + conjugate + fluorescent label
used in wash step and dilutions
PBS
fluorescent labels
FITC
rhodamine
darkens background
counterstain
major interference with IFA
rheumatoid factor (IgM anti-IgG)
an anti-IgM conjugate binds to RF and causes false pos
camouflages pt IgG, making it look like IgM
resolve RF interference
neutralize/adsorb RF or patient IgG when doing an anti-IgM assay
other interferences with IFA
- light exposure — must be kept in dark when running, as fluorochrome is light-sensitive
- insufficient washing — Ab not bound to slide may remain — false positives
- drying out — need to be kept in a moist chamber while they sit — does not wash as well when dried out, false positives
- reading of samples
reflex for any positive IFA
titer
serial dilution; most often twofold, but may begin with a higher dilution
QC requirement for IFA
positive and negative control on every slide you read (no matter how many wells on a slide)
may dilute out positive control to its endpoint (compare pt to the weakest positive)
sample requirements for IFA
- usually use serum — red top
- generally good for a few days in the refrigerator
- generally good for weeks in the freezer, but no re-freezing (may go back in refrigerator)
HEP-2 substrate used for…
ANA
MSK substrate used for…
- ASMA
- APCA
- AMA
Crithidia lucilliae substrate used for…
anti-nDNA
AMA fluorescence pattern
kidney tubules and parietal cells
cannot determine if an APCA is also present
C. lucilliae fluorescence pattern
kinetoplast (holds DNA); basal body may fluoresce, but not important
speckled + reflex
extractable nuclear antigen by EIA
4 ENA results and significance
- Smith (Sm) —lupus
- Ribonucleoprotein (RNP) —mixed connective tissue disease, lupus
- SSA, SSB —Sjogren’s syndrome A and B
significance of anti-ssDNA
anti-ssDNA = anti-histones
seen in drug-induced lupus
d/c drug
all of nucleus fluoresces
mitotic cells +
homogeneous
lupus, sometimes MCTD
reflex anti-nDNA
spotted nuclei
mitotic cells =
speckled
reflex to ENA
ladder-like appearance
mitotic cells +
centromere
CREST syndrome
no reflex
large spots in nuclei
mitotic cells +
nucleolar
progressive systemic sclerosis
outline of nuclei
mitotic cells +
peripheral/rim
highly specific for lupus
spindle apparatus
spindle pattern
no clinical significance
anti-nDNA seen in…
lupus
disease associations for Abs tested for on MSK
ASMA – chronic active hepatitis
AMA – primary biliary cirrhosis
APCA – pernicious anemia
Hgb is —- charged and migrates…
negatively
toward the +
hgb electrophoresis interferences
- application of sample — if you touch gel with pipette, it won’t be as smooth/even, and may add things to gel
- gels can melt or dry out
- gels must be stored flat
- wrong voltage
- pH of buffer and gel must be correct; can changes charges on proteins
abnormal C/A2 band
reflex to A2 column chromatography
explain A2 column chromatography
- pt hemolysate passes through a positively charged resin
- eluting buffer added to pull out hgb A2, which drips out into a tube
- may not remove all of A2, particularly when hgb S is present
- can be measured with spectrophotometry
functions of reagents in Hgb electrophoresis:
buffer strips
stain
wash solution
destain solution
buffer strips — carries hgb through gel
stain — binds to hgb
wash solution — washes away extra stain
destain solution — clears background of stain
hgb electrophoresis QC
every strip has to have an AFSC control; normal control not required but often performed
column chromatography requires a normal and abnormal control
Hgb electrophoresis sample requirements
- whole blood in EDTA
- in refrigerator, minimally good for 3-4 days
- should not be frozen
- if an unstable hgb is suspected, run w/i 24 hours
cellulose acetate gel
alkaline gel
citrate agar
acid gel
alkaline gel migration pattern
++ A F S C =
with S: Hgb D, Hgb G, Hgb Lepore
with C: Hgb A2, Hgb E, Hgb O
Hgb H and Hgb Bart migrate before A (fast)
4 beta chains, adults
4 gamma chains, babies
hgb H
hgb bart
reflex with abnormal hgb electrophoresis
acid gel
possibly A2 chromatography
sickledex with Hgb S +
acid gel migration pattern
++ C S A F =
Hgb A2 migrates with A
normal adult hgbs
97% A
3% A2
<1% F
no A, increased F and A2
beta thal major
some A, increased A2
beta thal minor
low A, increased F
baby