12.2 STI Screening: Chlamydia, Gonorrhea, Syphilis & Trichomoniasis

ABFM Family Medicine Certification Study Guide Exam

Track your progress as you read

Finished sections get a check mark.

1 Chapter 1: Exam Structure, Blueprint & Clinical Decision-Making

1.1 Exam Blueprint, FMCLA vs. One-Day Exam & Board Scoring 1.2 Clinical Reasoning, Test-Taking Strategy & Ambiguity Management 1.3 Evidence-Based Medicine & Clinical Practice Guidelines in Primary Care

2 Chapter 2: Healthcare Systems, Practice Management & Quality

2.1 Practice Management, Billing, Coding & Documentation 2.2 Quality Improvement, Patient Safety & Diagnostic Stewardship 2.3 Interprofessional Team-Based Care & Care Coordination

3 Chapter 3: Ethics, Law, Biostatistics & Health Equity

3.1 Medical Ethics, Informed Consent & Surrogate Decision-Making 3.2 Biostatistics, Clinical Epidemiology & Diagnostic Test Interpretation 3.3 Social Determinants of Health, Health Equity & Cultural Humility 3.4 Physician Wellness, Burnout Prevention & Professionalism

4 Chapter 4: Lifestyle Counseling & Behavior Change

4.1 Alcohol Use Screening & Brief Intervention 4.2 Illicit Drug & Cannabis Counseling 4.3 Tobacco & Vaping Cessation Counseling

5 Chapter 5: Nutrition, Physical Activity & Chronic Disease Prevention

5.1 Dietary Counseling for Obesity & Chronic Disease Prevention 5.2 Exercise Prescription & Physical Activity Counseling 5.3 Genetic Risk Assessment & Family History Counseling

6 Chapter 6: Routine Adult Immunizations

6.1 ACIP Adult Respiratory Vaccines: Influenza, COVID-19, RSV & Pneumococcal 6.2 ACIP Adult Non-Respiratory Vaccines: Tdap, Shingrix, HPV & Hep B 6.3 Immunizations in Special Populations: Pregnancy, Asplenia & Immunocompromise

7 Chapter 7: Pediatric Health Maintenance & Surveillance

7.1 Newborn Examination & Early Postnatal Care 7.2 Well-Child Care, Developmental Surveillance & Milestones 7.3 Pediatric & Adolescent Screening: Vision, Hearing, Anemia & Lead 7.4 Pediatric Oral Health, Dental Screening & Fluoride

8 Chapter 8: Behavioral Health & Safety Screening

8.1 Primary Care Depression, Anxiety & Behavioral Health Screening 8.2 Domestic Violence, Intimate Partner Violence & Firearm Safety 8.3 Occupational Health & Recreational Safety Counseling

9 Chapter 9: Adult Preventive Screening: Cardiovascular & Metabolic

9.1 Cardiovascular Disease & Hypertension Screening 9.2 Type 2 Diabetes Screening & Prediabetes Risk Stratification 9.3 Abdominal Aortic Aneurysm & Osteoporosis Screening

10 Chapter 10: Adult Cancer Screening: Breast & Gynecologic

10.1 Breast Cancer Screening & Risk-Assessment 10.2 Cervical Cancer Screening & ASCCP Algorithms 10.3 Skin Cancer Clinical Assessment & Counseling

11 Chapter 11: Adult Cancer Screening: Colorectal, Lung & Prostate

11.1 Colorectal Cancer Screening Modalities & Intervals 11.2 Lung Cancer Screening with Low-Dose CT 11.3 Prostate Cancer Screening & Shared Decision-Making

12 Chapter 12: Sexual Health, Infectious Disease Screening & Contraception

12.1 Sexual Health Counseling & Risk-Reduction Strategies 12.2 STI Screening: Chlamydia, Gonorrhea, Syphilis & Trichomoniasis 12.3 Bloodborne Infectious Disease Screening: HIV & Hepatitis C

13 Chapter 13: Reproductive Life Planning, Lactation & Preoperative Care

13.1 Preconception Planning & Comprehensive Contraception Management 13.2 Lactation Support & Breastfeeding Counseling 13.3 Preoperative Medical Evaluation & Pre-Participation Sports Exam

14 Chapter 14: Emergent Cardiovascular Conditions

14.1 Acute Coronary Syndromes & Myocardial Infarction 14.2 Acute Chest Pain Risk Stratification & Triage 14.3 Acute or Critical Valvular Heart Emergencies

15 Chapter 15: Cardiac Arrhythmias, Heart Failure & Hypertensive Crises

15.1 Acute Atrial & Ventricular Arrhythmias 15.2 Acute Decompensated Heart Failure & Cardiogenic Shock 15.3 Hypertensive Emergency & Urgency Management

16 Chapter 16: Vascular & Thromboembolic Emergencies

16.1 Pulmonary Embolism & Deep Vein Thrombosis 16.2 Acute Aortic Syndromes & Peripheral Vascular Emergencies 16.3 Critical Limb Ischemia & Acute Arterial Occlusion

17 Chapter 17: Neurologic Emergencies: Stroke & Altered Consciousness

17.1 Acute Ischemic Stroke & Intracranial Hemorrhage 17.2 Syncope Evaluation & Status Epilepticus 17.3 Acute Delirium, Encephalopathy & Severe Confusion

18 Chapter 18: Neurologic Trauma & Acute Cranial Emergencies

18.1 Concussion, Moderate-to-Severe TBI & Intracranial Injury 18.2 Thunderclap & Acute Severe Secondary Headaches 18.3 Acute Ophthalmologic Emergencies

19 Chapter 19: Acute Abdominal, Pelvic & Gastrointestinal Emergencies

19.1 Acute Abdominal & Pelvic Pain Triage 19.2 Upper & Lower Gastrointestinal Bleeding 19.3 Acute Hepatic Failure, Cholangitis & Severe Jaundice

20 Chapter 20: Acute Pulmonary & Airway Emergencies

20.1 Acute Hypoxic Respiratory Failure & ARDS 20.2 Severe Community-Acquired Pneumonia & Empyema 20.3 Acute Severe Epistaxis & Airway Obstruction

21 Chapter 21: Acute Traumatic Injuries & Wound Care

21.1 Major Trauma Resuscitation & Initial Assessment 21.2 Burn Assessment, Inhalation Injury & Resuscitation 21.3 Laceration Management, Complex Wounds & Animal Bites

22 Chapter 22: Acute Orthopedic & Musculoskeletal Emergencies

22.1 Acute Ambulatory Fractures & Initial Splinting 22.2 Compartment Syndrome & Major Orthopedic Trauma 22.3 Septic Arthritis & Acute Microcrystalline Crises

23 Chapter 23: Severe Infections, Sepsis & Systemic Emergencies

23.1 Sepsis, Septic Shock & Initial Fluid Resuscitation 23.2 Necrotizing Soft Tissue Infections & Severe CNS Infections 23.3 Anaphylaxis Diagnosis, Epinephrine Dosing & Airway Protection

24 Chapter 24: Metabolic, Endocrine & Electrolyte Emergencies

24.1 Diabetic Ketoacidosis & Hyperosmolar Hyperglycemic State 24.2 Critical Electrolyte Emergencies: Dyskalemias & Dysnatremias 24.3 Severe Calcium Abnormalities & Acute Adrenal Crisis

25 Chapter 25: Hematologic, Urologic & Dental Emergencies

25.1 Severe Symptomatic Anemias & Coagulopathic Emergencies 25.2 Testicular Torsion, Priapism & Acute Urinary Retention 25.3 Urgent Odontogenic Infections & Dental Trauma

26 Chapter 26: Psychiatric, Behavioral & Obstetric/Gynecologic Emergencies

26.1 Suicidal Ideation, Acute Agitation & Behavioral Emergencies 26.2 Acute Physical & Sexual Assault Care 26.3 Life-Threatening Vaginal Bleeding & Ectopic Pregnancy 26.4 Environmental Heat Stroke & Severe Hypothermia

27 Chapter 27: Acute Head, Neck & Neurologic Symptoms

27.1 Primary Acute Headaches: Migraine, Tension & Cluster 27.2 Concussion & Minor Closed Head Injury Evaluation 27.3 Transient Ischemic Attack Evaluation & ABCD2 Risk Scoring

28 Chapter 28: Acute Cranial Nerves, Hearing & Sensory Symptoms

28.1 Peripheral Neuropathies: Bell's Palsy, Carpal Tunnel & Radiculopathy 28.2 Acute Tinnitus, Sudden Sensorineural Hearing Loss & Cerumen Impaction 28.3 Acute Dizziness, Benign Paroxysmal Positional Vertigo & Vestibular Neuritis

29 Chapter 29: Acute Upper Respiratory Tract Infections

29.1 Acute Viral Rhinosinusitis vs. Bacterial Rhinosinusitis 29.2 Acute Pharyngitis: Group A Streptococcus & Centor Criteria 29.3 Acute Otitis Media, Otitis Externa & Serous Effusion

30 Chapter 30: Acute Lower Respiratory Infections & Cough

30.1 Influenza, COVID-19 & Viral Respiratory Syndromes 30.2 Acute Bronchitis & Lower Respiratory Tract Infections 30.3 Ambulatory Community-Acquired Pneumonia

31 Chapter 31: Allergic, Nasal & Non-Infectious Pulmonary Conditions

31.1 Allergic Rhinitis & Acute Non-Anaphylactic Allergic Reactions 31.2 Acute Dyspnea in Ambulatory Care 31.3 Interstitial Lung Diseases & Sarcoidosis Presentation

32 Chapter 32: Acute Chest, Cardiac & Vascular Symptoms

32.1 Palpitations Evaluation & Arrhythmia Triage in Primary Care 32.2 Deep Vein Thrombosis & Superficial Thrombophlebitis 32.3 Ambulatory Hypotension & Orthostasis Evaluation

33 Chapter 33: Acute Upper Gastrointestinal Conditions

33.1 Peptic Ulcer Disease & Gastritis 33.2 Dysphagia, Esophagitis & Acute Esophageal Disorders 33.3 Acute Nausea, Vomiting & Foodborne Illness

34 Chapter 34: Acute Lower Gastrointestinal Conditions

34.1 Acute Infectious Diarrhea & Gastroenteritis 34.2 Acute Constipation & Functional Bowel Changes 34.3 Ano-Rectal Disorders: Hemorrhoids, Fissures, Abscesses & Pruritus Ani

35 Chapter 35: Inflammatory, Functional & Malabsorptive GI Disorders

35.1 Acute Flares of Inflammatory Bowel Disease 35.2 Irritable Bowel Syndrome: Diagnosis, Subtyping & Management 35.3 Celiac Disease & Malabsorption Syndromes

36 Chapter 36: Acute Abdominal, Hepatic & Biliary Disorders

36.1 Ambulatory Abdominal & Pelvic Pain Triage 36.2 Acute Cholecystitis, Biliary Colic & Pancreatitis 36.3 Acute Liver Injury & Viral Hepatitis

37 Chapter 37: Acute Abdominal Wall, Hernias & Dental Conditions

37.1 Abdominal Wall, Inguinal & Ventral Hernias 37.2 Acute Dental Pain, Odontogenic Abscess & Aphthous Ulcers 37.3 Acute Edema: Unilateral vs. Bilateral Diagnostic Evaluation

38 Chapter 38: Acute Infectious Dermatoses

38.1 Bacterial Skin Infections: Impetigo, Cellulitis & Cutaneous Abscesses 38.2 Fungal Skin Infections: Tinea Corporis, Cruris, Pedis & Onychomycosis 38.3 Viral Cutaneous Infections: Herpes Simplex, Zoster & Molluscum Contagiosum

39 Chapter 39: Inflammatory, Allergic & Autoimmune Dermatoses

39.1 Atopic Dermatitis, Contact Dermatitis & Eczematous Flares 39.2 Non-Infectious Rashes: Urticaria, Drug Eruptions & Erythema Multiforme 39.3 Cutaneous Malignancies & Premalignant Lesions: AK, BCC, SCC & Melanoma

40 Chapter 40: Acute Shoulder, Elbow & Upper Extremity Injuries

40.1 Rotator Cuff Pathology, Tendinopathy & Shoulder Impingement 40.2 Lateral & Medial Epicondylitis, Olecranon Bursitis & Elbow Sprains 40.3 Wrist & Hand Soft-Tissue Injuries: De Quervain, TFCC & Finger Sprains

41 Chapter 41: Acute Knee, Ankle & Lower Extremity Injuries

41.1 Meniscal Tears, Ligamentous Knee Injuries & Patellofemoral Pain 41.2 Ankle Sprains, Ottawa Ankle Rules & Achilles Tendinopathy 41.3 Plantar Fasciitis, Shin Splints & Overuse Syndromes

42 Chapter 42: Acute Ambulatory Fractures & Dislocations

42.1 Distal Radius, Scaphoid & Common Upper Extremity Fractures 42.2 Metatarsal, Clavicle & Common Lower Extremity Fractures 42.3 Joint Dislocation Management: Nursemaid's Elbow & Shoulder Subluxation

43 Chapter 43: Acute Axial Musculoskeletal Pain & Falls

43.1 Acute Low Back Pain: Red Flags, Strain & Disc Herniation 43.2 Acute Cervical Strain, Whiplash & Axial Neck Pain 43.3 Evaluation of Falls in Ambulatory & Older Patients

44 Chapter 44: Acute Inflammatory Arthropathies & Generalized Pain

44.1 Acute Inflammatory Arthritis & Spondyloarthropathies 44.2 Myalgias, Rhabdomyolysis & Post-Viral Pain Syndromes 44.3 Acute Non-Headache Pain Management Strategies

45 Chapter 45: Acute Renal, Urinary & Genitourinary Conditions

45.1 Uncomplicated UTI, Pyelonephritis & Acute Urethritis 45.2 Hematuria Workup & Glomerulonephritis 45.3 Nephrolithiasis & Acute Urinary Tract Obstruction

46 Chapter 46: Acute Male Genitourinary & Prostatic Conditions

46.1 Acute Prostatitis, Epididymitis & Orchitis 46.2 Acute Scrotal Pain: Torsion vs Appendage, BPH & Male Genital Emergencies 46.3 Acute Urinary Retention & Incontinence Evaluation

47 Chapter 47: Acute Women's Health & Early Pregnancy Care

47.1 Early Pregnancy Diagnosis, Dating & Initial Complications 47.2 Abnormal Uterine Bleeding & Acute Menstrual Disorders 47.3 Premenstrual Syndrome & Premenstrual Dysphoric Disorder

48 Chapter 48: Breast Disorders, STIs & Pediatric Elimination

48.1 Palpable Breast Mass, Mastitis & Nipple Discharge 48.2 Sexually Transmitted Infections: Diagnosis, Staging & CDC Guidelines 48.3 Pediatric Enuresis & Encopresis

49 Chapter 49: Systemic Signs, Metabolic Dysregulation & Miscellaneous Infections

49.1 Acute Fever, Sepsis Screening & FUO in Primary Care 49.2 Acute Hyperglycemia & Symptomatic Hypoglycemia 49.3 Electrolyte Abnormalities: Mild-to-Moderate Disturbances 49.4 Vector-Borne, Tick-Borne & Rickettsial Illnesses

50 Chapter 50: Chronic Cardiovascular Diseases: Hypertension & Ischemia

50.1 Essential Hypertension Management: 2025 AHA/ACC Guideline & JNC Strategies 50.2 Chronic Coronary Artery Disease & Post-MI Secondary Prevention 50.3 Chronic Heart Failure: HFrEF, HFpEF & Quadruple GDMT

51 Chapter 51: Chronic Vascular, Valvular & Dyslipidemic Diseases

51.1 Peripheral Arterial Disease & Claudication 51.2 Chronic Valvular Heart Disease & Murmur Evaluation 51.3 Lipid Disorders & ASCVD Risk-Based Statin Therapy

52 Chapter 52: Chronic Respiratory Diseases: Asthma & COPD

52.1 Chronic Asthma Management: GINA Stepwise SMART Therapy 52.2 Chronic Obstructive Pulmonary Disease: GOLD Recommendations 52.3 Solitary Pulmonary Nodule Evaluation & Fleischner Society Criteria

53 Chapter 53: Chronic Metabolic Diseases: Diabetes Mellitus

53.1 Type 2 Diabetes Management: ADA Pharmacotherapy Algorithms 53.2 Type 1 Diabetes: Basal-Bolus Insulin, CGMs & Diabetic Complications 53.3 Diabetic Microvascular & Macrovascular Disease Surveillance

54 Chapter 54: Obesity, Nutrition & Metabolic Bone Diseases

54.1 Medical & Behavioral Management of Obesity & Incretin Mimetics 54.2 Osteoporosis & Metabolic Bone Disease: DEXA, FRAX & Antiresorptives 54.3 Nutritional Deficiencies: Vitamin D, B12, Iron & Malnutrition

55 Chapter 55: Chronic Endocrine Disorders

55.1 Primary & Subclinical Hypothyroidism, Hyperthyroidism & Nodules 55.2 Adrenal Disorders: Addison's Disease & Cushing's Syndrome 55.3 Hypercalcemia, Hyperparathyroidism & Pituitary Disorders

56 Chapter 56: Chronic Kidney Disease & Venous Disorders

56.1 Chronic Kidney Disease: KDIGO Staging & Renoprotective Therapy 56.2 Chronic Venous Insufficiency, Stasis Dermatitis & Lymphedema 56.3 Chronic Electrolyte & Acid-Base Management in CKD

57 Chapter 57: Chronic Gastrointestinal & Hepatic Diseases

57.1 Gastroesophageal Reflux Disease, Barrett's Esophagus & Dyspepsia 57.2 Chronic Liver Disease: MASLD/NAFLD, Cirrhosis & Portal Hypertension 57.3 Viral Hepatitis B & C: Long-Term Monitoring & DAA Therapy

58 Chapter 58: Colorectal Surveillance & Chronic Pancreaticobiliary Care

58.1 Post-Polypectomy Colorectal Polyp Surveillance Guidelines 58.2 Chronic Pancreatitis & Exocrine Pancreatic Insufficiency 58.3 Chronic Nausea, Gastroparesis & Functional GI Disorders

59 Chapter 59: Chronic Musculoskeletal & Rheumatologic Disorders

59.1 Osteoarthritis: Hip, Knee & Hand Management 59.2 Spinal Conditions: Spinal Stenosis, Spondylolisthesis & Compression Fractures 59.3 Chronic Myopathies & Fibromyalgia Syndrome

60 Chapter 60: Chronic Neurologic & Neurodegenerative Disorders

60.1 Dementia: Alzheimer's, Vascular & Lewy Body Disease 60.2 Parkinson's Disease & Essential Tremor 60.3 Epilepsy: Chronic Antiseizure Medications & Post-Stroke Care

61 Chapter 61: Chronic Peripheral Nerves, Pain & Sensory Disorders

61.1 Diabetic & Chronic Peripheral Neuropathies 61.2 Chronic Pain Syndromes & Chronic Daily Headaches 61.3 Chronic Tinnitus, Presbycusis & Persistent Dizziness

62 Chapter 62: Chronic Psychiatric Disorders

62.1 Major Depressive Disorder & Generalized Anxiety Disorder 62.2 Bipolar Disorder: Maintenance Pharmacotherapy & Lithium Monitoring 62.3 Adult & Pediatric Attention-Deficit/Hyperactivity Disorder

63 Chapter 63: Chronic Behavioral Health & Neurodevelopmental Conditions

63.1 Chronic Behavioral Conditions: PTSD, OCD & Somatization 63.2 Autism Spectrum Disorder & Intellectual Disabilities 63.3 Eating Disorders: Anorexia Nervosa, Bulimia & Binge Eating

64 Chapter 64: Chronic Substance Use Disorders & Tobacco Cessation

64.1 Alcohol Use Disorder: Pharmacotherapy & Relapse Prevention 64.2 Opioid & Stimulant Use Disorders: MOUD & Harm Reduction 64.3 Longitudinal Tobacco Cessation Pharmacotherapy

65 Chapter 65: Chronic Dermatologic Conditions

65.1 Acne Vulgaris, Rosacea & Seborrheic Dermatitis 65.2 Chronic Plaque Psoriasis & Biologic Therapies 65.3 Chronic Eczema, Hidradenitis Suppurativa & Cutaneous Lupus

66 Chapter 66: Chronic Reproductive, Infectious & Geriatric Special Care

66.1 Chronic Menstrual Disorders, Infertility & Sexual Dysfunction 66.2 Menopause Management & Hormone Replacement Therapy 66.3 Chronic HIV Infection Management & Primary Care Integration 66.4 Gender-Affirming Primary Care & Hormone Therapy 66.5 Advance Care Planning, Palliative Care & End-of-Life Symptom Control

67 Chapter 67: Continuity Care: Sleep, Fatigue, Cancer, Pregnancy & the Adult Preventive Visit

67.1 Chronic Insomnia & Obstructive Sleep Apnea 67.2 Chronic Malaise, Fatigue & ME/CFS 67.3 Primary Care During Cancer Treatment & Survivorship 67.4 Routine Prenatal Care & Longitudinal Pregnancy Management 67.5 The Periodic Adult Health Examination & Medicare Annual Wellness Visit

12.2 STI Screening: Chlamydia, Gonorrhea, Syphilis & Trichomoniasis

Key Takeaways Explain This Topic AI

The USPSTF recommends annual chlamydia and gonorrhea screening for all sexually active females aged 24 years and younger (Grade B) and for females aged 25 years and older who are at increased risk.

In men who have sex with men (MSM), screening requires multi-site Nucleic Acid Amplification Testing (NAAT) of the urogenital, rectal, and pharyngeal mucosa at least annually (and every 3 to 6 months for high-risk individuals), as >70% of extragenital infections are asymptomatic and missed by urine screening.

Syphilis screening (USPSTF Grade A in high-risk individuals and all pregnant persons) utilizes either the traditional algorithm (non-treponemal test reflexing to treponemal test) or reverse sequence algorithm (automated treponemal immunoassay reflexing to quantitative non-treponemal RPR, with TP-PA for discordant samples).

The prozone phenomenon is an antibody-excess artifact that causes a false-negative non-treponemal (RPR/VDRL) result in primary or secondary syphilis, which resolves upon laboratory dilution of the serum sample.

Expedited Partner Therapy (EPT) is an evidence-based clinical practice legally authorized in most states that permits clinicians to prescribe therapy (cefixime plus doxycycline) for the sexual partners of patients diagnosed with chlamydia or gonorrhea without prior clinician examination to prevent reinfection.

Last updated: September 2026

USPSTF Screening Guidelines: Chlamydia & Gonorrhea

Sexually transmitted infections caused by Chlamydia trachomatis and Neisseria gonorrhoeae are the two most common reportable bacterial infections in the United States. Untreated infections in females can ascend to the upper reproductive tract, causing Pelvic Inflammatory Disease (PID), tubal scarring, ectopic pregnancy, chronic pelvic pain, and tubal factor infertility.

The Evidence-Based Screening Mandates

Sexually Active Females Aged <=24 Years (USPSTF Grade B) : The USPSTF recommends annual screening for chlamydia and gonorrhea in all sexually active females aged 24 years and younger, regardless of reported symptoms or number of partners. High incidence rates and the predominantly asymptomatic nature of endocervical infections in young females justify universal annual screening.

Sexually Active Females Aged >=25 Years at Increased Risk (USPSTF Grade B) : The USPSTF recommends screening in females aged 25 and older who exhibit increased risk behaviors:

A new sexual partner or multiple sexual partners in the preceding 6 months.

A sexual partner diagnosed with a concurrent STI.

Inconsistent condom use during non-monogamous relationships.

Exchanging sex for money, housing, or drugs (commercial sex work).

A documented history of a prior bacterial STI within the past 12 months.

Men Who Have Sex with Men (MSM) : The CDC recommends at least annual screening for all sexually active MSM at all anatomical sites of exposure (pharyngeal, rectal, and urogenital). For high-risk MSM (multiple or anonymous partners, concurrent methamphetamine or substance use, or those taking HIV PrEP), screening should be performed every 3 to 6 months .

Pregnant Persons (USPSTF Grade B) : Universal screening for chlamydia and gonorrhea at the initial prenatal visit for all pregnant females aged <=24 years and older pregnant individuals at increased risk. For patients with persistent or new high-risk behaviors, repeat screening during the third trimester (ideally at 28 to 32 weeks) is mandated to prevent neonatal conjunctivitis (ophthalmia neonatorum) and chlamydial infant pneumonia.

Asymptomatic Heterosexual Men (USPSTF Grade I) : The USPSTF concludes that evidence is insufficient to assess the balance of benefits and harms of routine screening in asymptomatic heterosexual cisgender men. However, testing is clinically recommended in high-prevalence settings (adolescent clinics, correctional facilities, STI clinics) and is mandatory whenever a sexual partner is diagnosed with an STI.

Diagnostic Modalities: Multi-Site NAAT & Extragenital Testing

Nucleic Acid Amplification Testing (NAAT) represents the diagnostic gold standard for Chlamydia trachomatis and Neisseria gonorrhoeae due to its exceptional sensitivity (>95% to 98%) and specificity (>98% to 99%).

Preferred Specimen Types

Cisgender Females : The single preferred specimen is a vaginal swab (either self-collected by the patient in the clinic or clinician-collected during an examination). Vaginal swabs have higher clinical sensitivity than endocervical swabs and significantly higher sensitivity than clean-catch urine. If a pelvic speculum examination is performed, an endocervical swab is an acceptable alternative.

Cisgender Males : The preferred specimen is first-catch urine (the initial 20 to 30 mL of the voided stream). Patients must be instructed not to clean the urethral meatus prior to collection and should have abstained from urinating for at least 1 hour prior to specimen collection to ensure adequate bacterial cell concentration.

The Imperative for Multi-Site Extragenital Testing (MSM)

In individuals engaging in receptive oral or receptive anal intercourse—particularly MSM and transgender individuals—urogenital screening alone is entirely inadequate:

High Prevalence of Isolated Extragenital Infection : More than 70% to 85% of rectal and pharyngeal chlamydial and gonococcal infections are completely asymptomatic .

Diagnostic Blind Spots : Studies demonstrate that in MSM, up to 70% of gonorrhea cases and 85% of chlamydia cases are localized exclusively to the pharynx or rectum . If a primary care physician relies solely on a urine NAAT screen, the overwhelming majority of infections will be missed, allowing continued transmission and progression.

Pharyngeal Gonorrhea & Antimicrobial Resistance : Pharyngeal N. gonorrhoeae represents a critical biological reservoir for the development of multidrug resistance due to horizontal genetic exchange with commensal Neisseria species in the oropharynx. Furthermore, pharyngeal tissue has lower vascular perfusion; oral third-generation cephalosporins (such as cefixime) have inadequate pharyngeal penetration and high clinical failure rates. Pharyngeal gonorrhea requires high-dose intramuscular Ceftriaxone 500 mg IM single dose (1,000 mg IM if patient weight >=150 kg).

Syphilis Screening: USPSTF Grade A Recommendations

Syphilis, caused by the spirochete Treponema pallidum , is a multi-system, chronic vascular and mucocutaneous infection. The USPSTF issues a Grade A recommendation for syphilis screening in:

All asymptomatic individuals at increased risk (MSM, persons living with HIV, individuals who exchange sex for money or drugs, persons in correctional facilities, and history of prior STIs).

All pregnant persons during each pregnancy : Universal screening at the first prenatal visit. For individuals at high risk (unstable housing, substance use, high community prevalence, multiple partners), guidelines mandate repeat screening twice more: at 28 weeks gestation and at the time of delivery .

Clinical Staging & Manifestations

Primary Syphilis : Characterized by the chancre —a solitary, painless, indurated, clean-based, highly infectious ulcer that appears at the site of inoculation approximately 10 to 90 days (average 21 days) post-exposure, accompanied by painless regional lymphadenopathy. Spontaneously heals within 3 to 6 weeks.

Secondary Syphilis : Develops 2 to 8 weeks after the chancre disappears, reflecting widespread hematogenous and lymphatic spirochetemia. Cardinal features include a non-pruritic, diffuse, erythematous maculopapular or pustular rash prominently involving the palms and soles ; condyloma lata (broad-based, moist, flat, highly infectious vegetative plaques in warm intertriginous and perineal folds); mucous patches (painless shallow mucosal erosions); generalized lymphadenopathy; patchy "moth-eaten" alopecia; and systemic constitutional symptoms (fever, malaise).

Latent Syphilis : Seropositive without clinical signs or symptoms. Subdivided into:

Early Latent : Infection acquired within the preceding 12 months (documented seroconversion or symptom history).

Late Latent : Infection acquired >12 months ago or of unknown duration.

Tertiary Syphilis : Occurs years to decades after untreated infection. Features gummatous lesions (destructive granulomatous lesions of skin and bone), cardiovascular syphilis (aortitis, aortic root dilation, aortic regurgitation, ascending aortic aneurysms), and late neurosyphilis (tabes dorsalis with sensory ataxia, Argyll Robertson pupils, general paresis). Neurosyphilis can occur at any clinical stage (e.g., syphilitic meningitis, ocular syphilis, otosyphilis).

Serologic Testing Algorithms: Traditional vs. Reverse Sequence

Because Treponema pallidum cannot be cultured on artificial media, diagnosis relies on serology. Primary care laboratories utilize two distinct diagnostic pathways: TRADITIONAL ALGORITHM:

• [Non-Treponemal Test (RPR or VDRL)]
• |
• If Reactive (Titer e.g., 1:32)
• v
• [Confirmatory Treponemal Test (TP-PA or FTA-ABS)]
• |
• +----+----+
• | |
• Reactive Non-Reactive
• (Syphilis (Biological False Positive)
• Confirmed)

REVERSE SEQUENCE ALGORITHM:

• [Automated Treponemal Immunoassay (EIA or CIA)]
• |
• If Reactive
• v
• [Quantitative Non-Treponemal Test (RPR)]
• |
• +----+----+
• | |
• Reactive Non-Reactive (Discordant!)
• (Active v
• Syphilis) [Second Different Treponemal Test (TP-PA)]
• |
• +----+----+
• | |
• Reactive Non-Reactive
• (Past Treated Syphilis (False-Positive EIA;
• OR Untreated Late Latent Syphilis Excluded)
• OR Early Primary)
• Comparative Analysis of Non-Treponemal vs. Treponemal Tests

Serologic Feature Non-Treponemal Tests (RPR, VDRL) Treponemal Tests (TP-PA, FTA-ABS, EIA, CIA)

Antigen Target Non-specific host cardiolipin, lecithin, and cholesterol Specific recombinant Treponema pallidum antigens

Measurement Format Quantitative titer (e.g., 1:1, 1:2, 1:4, 1:8, 1:16, 1:32...) Qualitative (Reactive vs. Non-Reactive)

Clinical Role Evaluates disease activity and monitors therapeutic response Confirms true treponemal infection

Post-Treatment Behavior Titers decline following effective antibiotic therapy; should decrease by fourfold (two dilutions) within 6 to 12 months Remains reactive for life in >85% of patients regardless of treatment

Biological False Positives Common (SLE, antiphospholipid syndrome, acute febrile illness, pregnancy, advanced age, IVDU; typically titers <=1:4) Rare (endemic yaws/bejel, severe autoimmune disease)

The Prozone Phenomenon

Definition : The prozone phenomenon is a laboratory artifact occurring in non-treponemal testing (RPR or VDRL) where an overwhelming excess of anti-cardiolipin antibodies prevents the formation of cross-linked antigen-antibody lattices, resulting in a falsely non-reactive (negative) test result in a patient with active, florid syphilis.

Clinical Setting : Most commonly encountered during secondary syphilis (where spirochetal burden and antibody production are extraordinarily high) and during pregnancy.

Primary Care Management : If a patient presents with classic secondary syphilis lesions (e.g., palmoplantar rash, condyloma lata, generalized adenopathy) but their initial RPR or VDRL is reported as non-reactive, the clinician must contact the laboratory and request serum dilution (e.g., 1:16, 1:64). Diluting the serum restores the stoichiometric balance between antigen and antibody, allowing visual flocculation and yielding the true, strongly reactive high-titer result.

Trichomoniasis Screening & Management

Trichomonas vaginalis is a flagellated, parasitic protozoan that represents the most prevalent non-viral STI globally.

Screening Indications (CDC Guidelines)

Women Living with HIV : Mandatory annual screening because trichomoniasis accelerates HIV genital viral shedding, increases HIV transmission to partners, and markedly elevates the risk of pelvic inflammatory disease.

High-Prevalence Clinical Settings : Correctional facilities, high-volume STI clinics, and individuals with multiple concurrent partners.

Symptomatic Patients : Females presenting with diffuse, malodorous, frothy, yellow-green vaginal discharge, vulvar irritation, dysuria, and dyspareunia. Physical examination reveals vaginal erythema and punctate cervical microhemorrhages ( "strawberry cervix" ; seen in ~2% to 5% of cases).

Diagnostic Modalities: The Inadequacy of Wet Mount Microscopy

Saline Wet Mount Microscopy : Historically widespread; identifies motile trichomonads with jerky, spinning motility and abundant polymorphonuclear leukocytes (WBCs). However, wet mount microscopy has a dismal diagnostic sensitivity of only 50% to 60% , and trichomonad motility halts within 10 to 20 minutes of room temperature exposure, causing high false-negative rates.

Nucleic Acid Amplification Testing (NAAT) : The diagnostic gold standard for trichomoniasis. NAAT (e.g., transcription-mediated amplification on vaginal swab or urine) exhibits >95% to 100% sensitivity and specificity . The CDC strongly recommends NAAT over wet mount whenever feasible.

Evidence-Based Treatment Guidelines

Cisgender Females : Metronidazole 500 mg orally twice daily for 7 days .

Critical Practice Update : A pivotal randomized controlled trial demonstrated that the historical single-dose regimen (Metronidazole 2 g PO single dose) resulted in a 19% treatment failure rate in females, whereas 7-day multi-dose therapy resulted in an 11% failure rate (a nearly 50% relative reduction in treatment failure). The single 2-g dose is no longer recommended for females .

Cisgender Males : Metronidazole 500 mg orally twice daily for 7 days (or Metronidazole 2 g PO single dose if adherence is compromised).

Alternative Regimen : Tinidazole 2 g orally as a single dose.

Patient Counseling : Patients must strictly avoid alcohol consumption during metronidazole therapy and for 24 hours after completion (72 hours for tinidazole) due to the risk of severe disulfiram-like ethanol reactions (nausea, vomiting, flushing, abdominal cramps, tachycardia).

Mandatory Re-Testing : All sexually active females treated for trichomoniasis must be re-screened with NAAT 3 months post-treatment due to high reinfection rates (~17% within 3 months).

Loading diagram... STI Diagnostic Pathways: Syphilis Algorithms & Expedited Partner Therapy (EPT)