Blood, Sweat and Smears: "A Year of mHam 2.0 – Three Observations"

Host: Dr. Brad Lewis, Medical Director, Machaon Diagnostics
Date: September 26, 2025

Episode Overview

In this special webinar episode, Dr. Brad Lewis reviews the first year of experience with Machaon Diagnostics’ modified HAM (mHam) test, a novel functional assay for diagnosing complement-mediated thrombotic microangiopathies (TMAs), especially atypical hemolytic uremic syndrome (aHUS). Dr. Lewis shares practical insights, key findings from the lab’s first 8-9 months using mHam 2.0, and thoughts on interpretation and future directions in TMA diagnosis.

Main Topics and Discussion Highlights

1. Background: Thrombotic Microangiopathies (TMA) and the Role of Testing

(00:26 - 05:40)

• TMAs encompass diverse disorders characterized by microangiopathic hemolytic anemia and thrombocytopenia, often with organ damage, particularly affecting kidneys.
• The diagnosis often begins clinically and is challenging due to overlapping features with other hematologic and systemic diseases.
• “Every time you see a case of anemia and thrombocytopenia in a sick patient, that is a thrombotic microangiopathy. Is that true? No, that is not true. Most of the time it's not… But I think every time you see a case of anemia and thrombocytopenia, you ought to at least stop for a split second and ask, could this be my chance to see a thrombotic microangiopathy?”
  — Dr. Lewis (02:30)

Key Diagnostic Criteria:

• Thrombocytopenia (may not always be severe)
• Microangiopathic hemolytic anemia (red cell fragmentation; ± schistocytes)
• Elevated LDH, low haptoglobin (noting haptoglobin’s acute phase reactivity)
• Signs of organ injury (especially renal)

2. Differential Diagnosis of TMA

(05:40 - 14:50)

• Dr. Lewis reviews the extensive differential for TMA, stressing rare but critical diagnoses due to significant therapeutic implications:
  • TTP, atypical HUS, Shiga toxin-induced HUS, congenital causes, heparin-induced thrombocytopenia, DIC, mechanical etiologies, malignant hypertension, autoimmune diseases (e.g., lupus, scleroderma), catastrophic APS, pregnancy-related TMAs, infections, malignancies, drugs, and transplant-associated TMA.
• Complement activation underpins many atypical forms and overlaps with immune and infectious triggers.

3. Complement System and the Basis for the Modified HAM Test

(14:50 - 18:50)

• Pathogenesis in aHUS largely involves unregulated activation of the terminal complement cascade, leading to cell destruction (especially renal endothelial).
• The original HAM test (for PNH) inspired the concept, but the mHam is fundamentally different:
  • Uses modified, bioluminescent immortal renal cells sensitive to complement.
  • Measures ability of patient serum to lyse these cells, thus reflecting pathogenic complement activity directly.
• “We took our red cells, not the patient's red cells, added the patient's serum… and looked to see if the patient's serum was able to lyse sensitized red cells. That turned out to be a difficult test to scale up. But a version of that, a next generation version of it, was to develop a bioluminescent immortal renal cell...”
  — Dr. Lewis (17:30)

Functional Design:

• Knockout of CD46 makes cells complement-sensitive.
• Heat-treated plasma, normal, and aHUS serum are used in assay-controls.
• A cutoff is defined: >60% cell destruction (≤40% viability) suggests abnormal complement activity.

4. Advantages Over Existing Testing

(18:50 - 22:30)

• mHam is a functional (not surrogate biomarker) assay, directly showing complement’s effect on renal cells.
• Compared to soluble C5b-9 (“soluble MAC”) assay:
  • mHam is more sensitive and specific for aHUS.
  • Sets apart aHUS and similar disorders from other complement-driven illnesses (lupus, scleroderma, sepsis, malignancy).
  • Useful even in patients in remission and when dealing with genetic VUS (variants of uncertain significance).
• “It appears to be both a bit more sensitive than the soluble MAC… and simultaneously more specific for aHUS.”
  — Dr. Lewis (22:30)

5. Results: First Year of mHam Use – Real-World Experience

(22:30 - 27:10)

• ~170 samples analyzed; most results were normal (reflecting the social phenomenon that the test is ordered mostly for cases where aHUS is a concern but not strongly suspected).
• No cases of aHUS with a negative mHam except those already on therapy.
• Cases discussed:
  • Lupus and HLH patients with elevated soluble MAC but negative mHam—not aHUS.
  • Renal TMA due to prostate abscess with normal results, resolved after abscess treatment.
• Value of mHam highlighted in clarifying diagnoses and avoiding misattribution to aHUS.

6. Soluble MAC Versus mHam – When to Use Each

(27:10 - 28:55)

• Soluble MAC is less expensive, has a studied role in predicting relapse risk (esp. at eculizumab trough), and can aid dose adjustments.
• mHam offers true functional insight but should only be done off-therapy due to normalization effects of treatment.
• “If I think somebody has aHUS, they still have aHUS [even with negative genetic testing]. Once I've decided, I go ahead and treat. If I'm really confused, my go to would be the modified HAM test…”
  — Dr. Lewis (28:42)

7. Laboratory Interference: Triglycerides

(28:55 - 30:36)

• High triglycerides can interfere, making an abnormal sample appear normal/equivocal.
• Even moderate elevations (1+ visually) shift results toward normal.
• Fortunately, visible triglycerides are rare (~0.5% of samples); visually screened and flagged.
• Ongoing research to eliminate this interference.

8. Questions & Clinical Pearls

(30:36 - 39:17)

On Interpretation & Practice

• Negative mHam in transplant-associated TMA? Dr. Lewis would still strongly consider treatment if criteria are met; not enough data yet in this subgroup.
• Rationale for cutoffs: Empirically derived; <60% viability is suspicious, <46.5% is highly specific for aHUS.
• Renal-limited TMA validation: Not validated in this setting—work in progress.
• Utility in sickle cell delayed hemolytic transfusion reaction: Not yet studied, but future research anticipated.
• What does “very positive” mean? Not clear; higher positivity may relate to more complement activity, but interpretation is still evolving.
• Preanalytic variables: mHam is robust, but samples should be processed, frozen promptly, and delivered with minimal mishandling.

On Access & Logistics

• Outpatient access can be a challenge, but Machaon tries to help with resources.
• mHam result = positive/negative plus percent viability. Not to be used in patients on therapy (unless for efficacy assessment).

Notable Quotes

• “Waiting for genetics is almost always a mistake in these cases… If you're really confused, my go to would be the modified hand test as a way of sorting that out.”
  — Dr. Lewis (28:42)
• "A positive [mHam] test clearly is useful. We've so far had no false positive tests."
  — Dr. Lewis (29:56)
• “If you send us a sample and we see triglycerides, you will get back a report noting that we don't trust this sample...”
  — Dr. Lewis (30:24)

Memorable Moments & Practical Takeaways

• The mHam test is a new, functional, and rapidly available assay that offers greater specificity for aHUS than currently available alternatives.
• Pre-treatment testing is ideal; therapy normalizes both mHam and soluble MAC, making them less useful for diagnosis.
• Visual/clinical vigilance is still required: test results must be interpreted in clinical context.
• Genetics are valuable but often negative; treatment should not be delayed awaiting results.
• Laboratory interference (esp. triglycerides) is rare, but samples with visible lipemia should be interpreted with caution or repeated.
• Machaon Diagnostics welcomes direct clinician queries for both logistical and interpretive support.

Timestamps for Key Segments

| Topic | Timestamp | |-------------------------------------------------|:-------------:| | What is TMA? Diagnostic pearls | 00:26 - 05:40 | | TMA differential diagnosis | 05:40 - 14:50 | | Complement cascade and mHam test design | 14:50 - 18:50 | | Functional vs surrogate assays | 18:50 - 22:30 | | Year-one data, practical insights | 22:30 - 27:10 | | Soluble MAC vs. mHam, clinical decisions | 27:10 - 28:55 | | Triglyceride interference | 28:55 - 30:36 | | Audience Q&A and clinical pearls | 30:36 - 39:17 |

Final Thoughts

Dr. Lewis’s session offers a candid, practical perspective on the mHam’s value in the real world and the evolving field of complement-mediated TMAs. The test is a promising addition to the diagnostic armamentarium, but best used thoughtfully, in context, and with attention paid to both technical and clinical nuances.

For clinicians: Don’t hesitate to reach out to Machaon Diagnostics for advice, access issues, or nuanced cases. Dr. Lewis and his team are keen to be partners in improving care for patients with rare and severe blood disorders.