---

Drunkometer in Forensic Medicine

What It Is

---

Basic Principle

2100 mL of alveolar air = 1 mL of blood in terms of alcohol content

---

Chemical Reaction (Classic Drunkometer)

• A dry balloon or plastic bag, OR
• Directly into a glass tube containing the reagent mixture

Ethyl alcohol + Dichromate (orange/yellow) → Greenish colour change

• The intensity of the green colour is proportional to the amount of alcohol present
• A BAC >80 mg% is considered a positive result (green colour) - PC Dikshit Textbook

---

Procedure

1. The person is asked to blow into a special container or directly into the breath analyser
2. 60-100 mL of exhaled (deep lung) breath is collected
3. The breath contacts the bichromate-sulfuric acid reagent
4. Colour change (yellow/orange → green) indicates the presence and amount of alcohol
5. This is a qualitative/semi-quantitative screening test

---

Causes of False Positive Results

---

Comparison with Other Samples for Alcohol Analysis

---

Legal / Medicolegal Significance

• The drunkometer/breathalyser is the primary roadside screening test used by police
• In India, the statutory blood alcohol limit is 30 mg% under Section 185, Motor Vehicles Act 1988
  • First offence: fine up to ₹5,000 or 6 months imprisonment or both
  • Subsequent offences: fine up to ₹3,000 or 2 years imprisonment or both
• Electronic breath analysers with printed output have been accepted for court work in some countries abroad
• A limitation: if alcohol absorption is not yet complete at the time of testing, BAC may be overestimated - Parikh's Textbook

---

Widmark Formula (Supplementary)

a = p × r × c

• a = weight of alcohol in the body (grams)
• p = body weight (kg)
• r = distribution constant (0.68 for males; 0.55 for females)
• c = concentration of alcohol in blood (mg/kg)

---

• The Essentials of Forensic Medicine and Toxicology, 36th ed.
• PC Dikshit Textbook of Forensic Medicine and Toxicology
• Parikh's Textbook of Medical Jurisprudence, Forensic Medicine and Toxicology

---

Systemic Lupus Erythematosus (SLE)

Definition

---

Epidemiology

---

Pathogenesis

Genetic Factors

• Multiple susceptibility genes (polygenic, cumulative-hit model)
• Impaired inactivation of the X-chromosome may explain the female predominance
• Strong HLA associations (HLA-DR2, HLA-DR3)
• Complement deficiencies (C1q, C2, C4) predispose to SLE

Environmental Triggers

• UV light - alters DNA methylation, generates stimulatory nucleic acids, activates keratinocyte immune responses
• Epstein-Barr virus - induces IFN response, expresses viral proteins activating SLE susceptibility genes
• Low socioeconomic status, mercury, pesticides, diet
• Gut microbiome - increased gut permeability promotes translocation of gut microbes, contributing to autoantibody development

Innate Immunity Defects

• Neutrophils have higher turnover in SLE, delivering large loads of stimulatory nucleic acids
• Defective macrophage/dendritic cell clearance of cellular debris and immune complexes
• Excess uncleared debris triggers nucleic acid sensors and TLRs in plasmacytoid dendritic cells
• Result: massive upregulation of type I interferon (IFN) - the "IFN signature" central to SLE

Adaptive Immunity Defects

• B cells lose tolerance - expand as "age-associated B cells (ABCs)" that mature into autoantibody-secreting plasma cells
• T follicular and T peripheral helper cells promote B-cell differentiation into high-affinity autoantibody plasma cells
• T regulatory cells are defective - cannot maintain tolerance
• Autoantibodies form immune complexes that deposit in tissues causing inflammation

---

Autoantibodies in SLE

Key rule: ANA sensitivity is >95% (excellent screening), but Anti-dsDNA and Anti-Sm are the most specific antibodies for SLE. - Harrison's 22e; Harriet Lane Handbook

---

Classification Criteria: 2019 EULAR/ACR

Classify as SLE if total score ≥ 10 points - Goldman-Cecil Medicine

---

Clinical Manifestations

Cutaneous (70-80%)

• Malar (butterfly) rash - erythema over cheeks and nose bridge, sparing nasolabial folds; triggered/worsened by UV
• Discoid lupus - chronic scarring plaques, may cause permanent alopecia
• Subacute cutaneous lupus (SCLE) - annular or papulosquamous lesions, associated with anti-Ro
• Photosensitivity
• Non-scarring alopecia - hair loss/thinning during flares
• Oral/nasal ulcers - usually painless
• Vasculitic lesions - Raynaud's phenomenon, livedo reticularis

Musculoskeletal (90%)

• Arthralgia and non-erosive arthritis - symmetrical, involving small joints (hands, wrists, knees)
• Jaccoud's arthropathy - reversible deformity due to tendon/ligament laxity (not erosive)
• Myalgia, myositis (less common)
• Osteonecrosis (avascular necrosis) - especially with steroid use

Renal (40-75%) - Lupus Nephritis

• One of the most serious manifestations
• WHO/ISN-RPS Classes:
  • Class I: Minimal mesangial
  • Class II: Mesangial proliferative
  • Class III: Focal proliferative (< 50% glomeruli)
  • Class IV: Diffuse proliferative (≥ 50% glomeruli) - most severe, worst prognosis
  • Class V: Membranous
  • Class VI: Advanced sclerosis
• Presents with haematuria, proteinuria, hypertension, nephrotic/nephritic syndrome

Neuropsychiatric (50%)

• Headache, cognitive dysfunction, "brain fog"
• Seizures, psychosis, stroke (often aPL-mediated)
• Peripheral neuropathy, myelitis

Cardiovascular

• Pericarditis (most common cardiac manifestation)
• Myocarditis, endocarditis (Libman-Sacks endocarditis - sterile verrucous vegetations on valve surfaces)
• Accelerated atherosclerosis - major cause of morbidity/mortality in long-term disease
• Raynaud's phenomenon

Pulmonary

• Pleuritis/pleural effusion (most common pulmonary manifestation)
• Pneumonitis, pulmonary hypertension
• "Shrinking lung syndrome" - diaphragmatic dysfunction

Hematologic

• Anemia - often autoimmune hemolytic; also anemia of chronic disease
• Leukopenia (lymphopenia is most characteristic)
• Thrombocytopenia

Antiphospholipid Syndrome (aPL)

• Present in ~30-40% of SLE patients
• Causes: venous/arterial thrombosis, recurrent miscarriage, thrombocytopenia
• Lab: lupus anticoagulant, anticardiolipin Ab, anti-β2GPI Ab

---

Treatment

Overview: Treat-to-Target Approach

• Goal: remission or lowest possible disease activity to prevent organ damage
• Hydroxychloroquine (HCQ) 5 mg/kg/day is the backbone of therapy for ALL patients unless contraindicated - reduces flares, damage, and mortality
• Minimize glucocorticoid exposure; taper as quickly as possible

Treatment by Severity

• NSAIDs (with caution - risk of aseptic meningitis, renal dysfunction)
• HCQ +/- low-dose glucocorticoids
• Methotrexate or azathioprine for steroid-sparing

• Glucocorticoids - IV methylprednisolone pulse for severe flares, then oral taper
• Mycophenolate mofetil (MMF) - first-line for lupus nephritis induction and maintenance
• Cyclophosphamide (CYC) - IV; used for severe nephritis (NIH regimen or Euro-lupus low-dose)
• Azathioprine (AZA) - maintenance therapy, safe in pregnancy
• Rituximab (RTX) - anti-CD20; for refractory disease

Biologics

• Belimumab (anti-BLyS/BAFF) - approved for active SLE and lupus nephritis; reduces flares; given as add-on to standard therapy with MMF or low-dose CYC
• Anifrolumab (anti-IFN receptor) - approved for moderate-to-severe SLE; particularly effective for skin disease; NOT recommended for severe neuropsychiatric disease
• Voclosporin (VOC) + MMF - calcineurin inhibitor combination for lupus nephritis

Lupus Nephritis Treatment Algorithm (EULAR 2024):

---

Type 1 vs Type 2 Lupus (Harrison's 22e Classification)

---

Prognosis & Monitoring

• Disease activity tracked with SLEDAI (SLE Disease Activity Index) or BILAG scores
• Anti-dsDNA titres and complement (C3/C4) levels correlate with disease activity
• Main causes of death: Infection (especially early), cardiovascular disease (atherosclerosis, especially late), renal failure, CNS disease
• Accelerated atherosclerosis is a major late complication; annual cardiovascular risk assessment recommended
• Blood for alcohol: serum fluoride/oxalate preserved; avoid spirit for skin cleaning (to prevent false-positive alcohol results - from forensic context this time, about SLE, not alcohol!)

---

• Harrison's Principles of Internal Medicine, 22nd ed. (2025) - primary reference
• Goldman-Cecil Medicine, International Edition - classification criteria, pathobiology
• Harriet Lane Handbook, 23rd ed. - autoantibody specificity/sensitivity