sFLC, the logical means of identifying monoclonal FLC in the event of poor urine sample provision

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sFLC, the logical means of identifying monoclonal
FLC in the event of poor urine sample provision?

• Dr Tracy J Lovatt
• Clinical Scientist, Immunology
• New Cross Hospital
• tracy.lovatt_at_rwh-tr.nhs.uk

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Traditional screening for LPD

• Measure IgG, IgA, IgM
• Serum protein or capillary zone electrophoresis
• Immunofixation of abnormal bands
• Urine electrophoresis and immunofixation for BJP.

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Urine electrophoresis
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Urine Immunofix
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Renal Metabolism of FLC
?FLC - 25 kDa ?FLC - 50 kDa
Glomerulus 40-60 kDa pores

• Renal metabolism
• Anuric
• Provision
• Smell

10-30g/day reabsorption breakdown
Urine
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Serum free light chain immunoassay
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Aim

• To determine whether sFLC could replace urine
  electrophoresis when screening for myeloma and
  other plasma cell dyscrasia?
• Calculate sensitivity/specificity for LPD

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Results n653

• 597 normal by SPE and FLC (91)
• 17 clear band and abnormal FLC (2.6)
• 21 paraprotein but normal FLC (3.2)
• 18 no band on SPE but abnormal FLC (2.5)

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Performance

• / -/- -/ /- Sensitivity Specificity
• FLC gt1.84 26 609 9 9 74.3 98.5
• SPE 23 602 12 16 65.7 97.4
• SPE FLC 35 597 0 21 100.0 96.6
• gt1.84

Test/Diagnosis Performance
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Results

• 30/653 had urine sample (4.6)
• 1/30 positive for BJP (amyloidosis)
• Dodgy ground?

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Obvious?

• For laboratories receiving lt5 urine samples
  arguing the relative merits of sFLC and urine BJP
  borders on the irrelevant.

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Whats the cost?

• Write to patient
• Return visit to hospital or GP
• Admin and cost of BJP and report
• Patient anxiety

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Normal range for sFLC ratio

• 0.26 - 1.65 Published reference range
• 0.25 1.84 Local reference range NX
• 8 results
• 1.65 1.84 (Crohns, RA, SLE, PMR)

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Normal SPE/ Abnormal FLC

• 12 /18 Lymphoproliferative Disorders
• 1 IgD Myeloma
• 1 IgA Myeloma/MGUS
• 6 CLL (1 undiagnosed at the time of screening)
• 4 FLC-MGUS
• 6/18 no LPD (0.2 0.22 0.25 1.92 1.97 2.0)

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Case 1 IgD Myeloma

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Case 1

• SPE - no obvious paraprotein
• Insufficient evidence to initiate IF
• Serum Free Light Chain Analysis
• Kappa 27.8mg/L
• Lambda 868mg/L
• Kappa/Lambda Ratio 0.003

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Case 1 IgD Myeloma

• IFE demonstrated the presence of an IgD Lambda
  paraprotein
• Patient referred to Haematologist
• Follow-up Investigations confirmed myeloma
• Patient refused follow up

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Case 2

• 73 yr old female
• Seen by GP with mobility issues
• Lab Results
• IgG 10.3(g/L)
• IgA 4.29 (g/L)
• IgM 1.1 (g/L)

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IgA paraprotein
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Case 2

• SPE - no obvious paraprotein
• Insufficient evidence to initiate IFE
• Serum Free Light Chain Analysis
• Kappa 72.8mg/L
• Lambda 14.6mg/L
• Kappa/Lambda Ratio 4.99

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Case 2 IgA Myeloma/MGUS

• IFE demonstrated IgA kappa band
• Hidden in Beta Region on SPE
• Since initial sample patient has had mild
  deterioration in renal function
• No significant change in patients condition
• Patient under evaluation to determine IgA
  Myeloma/MGUS

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Freelite
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Another case

• 69 yrs, female
• Presented Jan 2008
• Lambda light chains on SPE/IF
• Fast track referral
• Light chain myeloma
• sFLC
• Kappa 9.2 mg/L
• Lambda 33 mg/L
• Ratio 0.28 (0.25 1.84)

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Antigen Excess

• Default dilution 1/100
• Retest at 1/2000
• Kappa 9.2 mg/L
• Lambda 7779 mg/L
• Ratio 0.001
• Normal range (0.25 1.84)

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October 2008

• Dilution 1/2000
• Kappa 10.2 mg/L
• Lambda 67.2 mg/L
• Ratio 0.15
• Normal range (0.25 1.84)

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30th March 2009

• Clinic
• Unwell
• Admitted ? relapse
• Kappa 6.17 mg/L
• Lambda 77.9 mg/L
• Ratio 0.08

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1st April 2009

• Question results
• Retest at 1/2000
• Kappa 6.17 mg/L
• Lambda 36432 mg/L
• Ratio 0.0001
• Rapid disease progression

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Aggressive

• Date Lambda mg/L
• 17.04.09 29,000
• 24.04.09 23,000
• 05.05.09 18,650

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Recommendations

• Useful to establish local reference range for
  sFLC
• Addition of sFLC to primary screen for
  paraproteinemia increases the sensitivity and
  improves specificity for LPD.
• Not for all Immunoglobulin requests

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Recommendations

• With poor urine provision it seems logical to
  add sFLC rather than request a urine sample.
• Check for antigen excess at 1/2000
• Antigen excess is patient specific

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Acknowledgements

• Ewan Robson, Claire Beardsmore, Joanne Taylor,
  Liz Laverick, Stephanie Cooper
• The Binding Site Ltd
• Graham Mead and Josie Hobbs.