Proteins

Question 1

What are the indications for SFLC measurement?

Answer 1

• For diagnosis and prognosis in plasma cell proliferative disorders; primary amyloidosis (AL), NSMM, LCMM, LCDD and solitary plasmacytoma
• monitoring response in multiple myeloma and/or oligosecretory diseases, NSMM, AL and LCDD.

Question 2

What is acceptable difference between total measured IgG and sum of the subclasses?

Answer 2

McLean Tooke 2013 Pathology
IgG sum within range of 20% greater than or 15% below total IgG

Above this range may be seen when IgG subclass other than IgG2 elevated

Question 3

What are the causes of discrepant IgG subclass/sum results?

Answer 3

Usually if IgG4 elevated
- due to antisera preferntial binding of IgG1

Exclude other interferences

• paraprotein
• rheumatoid factor (binding IgG and interfering)
• cryoglobulin

Also random error

• pre analytical
• analytical; sampling, reagent, calibrator, QC
• instrument
• post analtyical

Question 4

What is the limit of detection for serum and urine EPG?

Answer 4

Serum <1g/L

Urine 0.01g/L

Measurement of pp by densitometry becomes inaccurate over 50g/L

Question 5

What are the methods used to detect IgE ?

And what are the differentials for a cause of high IgE?

Answer 5

chemiluminescence
nephelometry
immunocap
radioimmunoassay

Atopy- eczema/FA/asthma
Infection; fungal ABPA, parasitic, helmnith, TB, HIV
vasculitis
IGE myeloma
Hyper IgE

Question 6

What are the principles of component resolved diagnosis for detection of allergen specific IgE? What are the advantages and disadvantages?

Answer 6

Allergens have specific and cross reactive components- may explain primary sensitiser /and other sensitisation that is not clinically significant

ISAC microarray is components on a chip multiplex, ? check native and recombinant allergens used

Advan: epitope specificity- IT/allergic profile, avoid unecessary anxiety, precision medicine, multplex, only small volume needed, automated, fast TAT , high precision due to triplicates

Disadv: expensive, long TAT, few labs doing this, may not be diagnostic still, cross reacting Abs false positive still, competition with IgG and IgE - false negatives, CV 30% due to inaccuracy of spotting

Question 7

What are limitations of SFLC compared to other methods of LC quantiation?

Answer 7

• ag excess
• high CV poor inter lab reproducibility
• FK/ may bind to other proteins overestimate

advan

• sensitiv 0.001g/L
• early relapse detector
• easy to perform
• fast TAT

Question 8

BAT activation markers

Answer 8

piecemeal degranulation
CD203c - exclusively on basophils (usually third makrer)

Anaphylactic
CD63

Need additional basophil markers CD123, CCR3, IgE

Needs whole blood, processed within 4 hours otherwsie reactivity decline

anti FceRI positive controls, stim buffer neg control

Question 9

Immunocap for drug allergy sens/spec

Answer 9

sens 0-50%
spec 84-100%
mainly for betalactams only

RIA/RAST
sens 50-75%
spec 70-83%

BAT
sens 50-78%
spec 88-97%

Question 10

What are some of the advan/disadvan of BAT?

Answer 10

Advan

• safety
• functional test
• good sens, spec
• for drugs not available on immunocap/skin testing due to irritation

Disadva

• cell viability
• ag conce for drugs
• drugs may need to be haptenated
• flow
• mostly IVD lack of standardised protocols

Question 11

What are some of the assays to test non immediate T cell mediated reactions?

Answer 11

• t cell proliferation radioactive
• t cell proliferation ; CFSE, cell and or cytokine marker expression
• upreg activation marker CD69, 25, 137
• ELISpot, secreted molecules + used with flow

Question 12

HLA association with drug reactions

Answer 12

abacavir- hypersensitivit HLAB 5701

allopurinol- SJS TENS
HLAB 5801

Carbamazepine SJS TENS
HLAB 1502
same for lamotrigine