Laboratory Testing for Hidradenitis Suppurativa
All patients with HS should undergo infectious disease screening (hepatitis B, hepatitis C, and tuberculosis) prior to initiating systemic immunomodulatory therapy, along with comorbidity screening for metabolic and cardiovascular risk factors 1.
Pre-Treatment Infectious Disease Screening
Before starting any biologic or systemic immunosuppressant therapy, mandatory screening includes 1:
- Hepatitis B surface antigen and antibodies
- Hepatitis C antibody
- Tuberculosis testing (interferon-gamma release assay or tuberculin skin test)
Additional location-specific and patient-specific screening should be considered based on:
- Endemic diseases in your geographic region
- High-risk occupations or activities
- Clinical assessment for uncommon infections (leprosy, leishmaniasis, strongyloidiasis in appropriate contexts)
This represents the first HS-specific consensus for pre-treatment screening, as previous recommendations were simply extrapolated from psoriasis guidelines 1.
Comorbidity Screening Labs
Given the strong associations with metabolic and cardiovascular disease, comorbidity screening should occur shortly after HS diagnosis 2, 3:
Metabolic Panel
- Fasting glucose or HbA1c (diabetes screening)
- Lipid panel (dyslipidemia screening)
- Basic metabolic panel
The rationale: HS patients have 1.5 times the risk of major adverse cardiovascular events compared to controls, and 3 times greater risk of carotid plaques 2.
Inflammatory Markers
While newer inflammatory biomarkers have been studied, C-reactive protein (CRP) remains the most clinically useful marker 4:
- CRP - correlates with disease severity and maintains clinical value
- ESR - may be considered but less specific
- Complete blood count with differential
Important caveat: Neutrophil-lymphocyte ratio (NLR), platelet-lymphocyte ratio (PLR), and similar derived ratios showed no significant correlation with HS severity in recent studies, despite their utility in other inflammatory conditions 4. The monocyte/HDL ratio (MHR) showed some correlation with disease duration but is not routinely recommended.
Additional Screening Based on Comorbidity Risk
Inflammatory Bowel Disease Screening
If patients report gastrointestinal symptoms, consider:
- Fecal calprotectin
- Referral to gastroenterology
HS patients have 3 times the risk of Crohn's disease and 1.3-1.8 times the risk of ulcerative colitis 2.
Spondyloarthritis Screening
If patients report back pain or joint symptoms:
- ESR/CRP
- Consider HLA-B27 if clinical suspicion is high
- Rheumatology referral
HS patients have 1.5-9.4 times greater odds of spondyloarthritis 2.
Clinical Pitfalls to Avoid
Do not mistake IgG4 elevation for IgG4-related disease: A recent case report documented persistent IgG4 elevation in severe HS that was initially misdiagnosed as IgG4-related disease, leading to inappropriate treatment 5. IgG4 elevation may represent a compensatory response to chronic inflammation in HS rather than a separate disease process. If IgG4 is incidentally elevated, ensure tissue biopsy confirmation before diagnosing IgG4-related disease.
Do not rely on novel inflammatory ratios for clinical decision-making: Despite theoretical appeal, most derived inflammatory markers (NLR, PLR, LHR, NHR) have not demonstrated clinical utility in HS management 4.
Timing Considerations
- At diagnosis: Comorbidity screening (metabolic panel, lipids, glucose)
- Before systemic therapy: Infectious disease screening panel
- During flares or hospitalization: CRP, CBC to assess inflammatory burden and guide treatment intensity 6
- Ongoing monitoring: Repeat metabolic screening annually given cardiovascular risk