STIs 2 Flashcards
(31 cards)
Which individuals are at increased risk of HIV?
MSM
IVDU
People from areas of the world where heterosexual HIV infection is endemic
blood/blood products/organ recipient between 1975-85
occupational and medical exposure via invasive procedures in unsterile conditions
What does a white curd like vaginal discharge suggest?
Candida
What does a watery/malodourous vaginal discharge suggest?
BV or TV
What does a mucopurulent vaginal discharge suggest?
Gonorrhoea
What does a white/clear vaginal discharge suggest?
Chlamydia/NSU
Which conditions is dysuria associated with?
chlamydia
gonorrhoea
TV
HSV
Which STD cause IBD/PCB?
CT and GC
Which STD causes genital ulcers?
Herpes simplex virus is the commonest cause in the UK
consider: primary syphillis (1ary painless chancre), traums, bacterial infection, carcinoma and tropical ulcer disease (LGV)
Which STDs are associated with lymphadenopathy?
HSV
HIV
What causes balanitis?
Inflammation of the glans can be caused by:
Candida/anaerobic bacteria
Which STDs cause epidymo-orchitis?
Swelling and tenderness of testes/epididymis
caused by:
CT, GC
or Gram -ve organisms
Which STDs cause pelvic pain and dyspareunia?
may suggest PID caused by CT, GC or anaerobes
What type of tests are used for gonorrhoea, and their sensitivity/specificity?
Microscopy - cervical (50%) and male urethral (95%)
NAAT - endocervical/urethral (95%), female urine samples (30-60%)
Culture - Gran -ve diplococci, oxidase +ve, utilises glucose. Antibiotic suseptibility - penicillinase activity or antibiotic discs on pure culture (85-95%)
Which samples are collected for chlamydia testing?
Urine and urethrel in men
Vaginal/cervical (rotate for 10-20s)
What tests are used to identify chlamydia?
Microscopy - PMNs
NAAT (97-98%)
Culture - expensive, labour intensive and time consuming and very few labs offer service. low sensitivity (75%) but can be 100% specific
EIA - easier than culture and more sensitive (but still only 70%) - may give false +ves so confirmation of +ve results essential
Direct Fluoroscence Ab (DFA) - monoclonal Ab binds to C.trachominits, identified using fluroroscence microscope
What tests are used to diagnose TV?
Remember TV -> vaginitis and green discharge
STD
Test:
Wet slide microscopy - motile protozoan and flagellae, associated with pH >4.5 (92% - sensitvity)
CULTURE is GOLD STANDARD, but it is difficult and time consuming - direct inoccula
What tests are used to diagnose candida?
Microscopy - Gram stained vaginal smear - PSEUDOHYPHAE and BUDDING YEAST (SPORES)
Culture: Direct innoculation on Sabouraud’s medium or into transport media - it is also commensal so results interpreted alongside clinical details
What tests are used to diagnose bacterial vaginosis?v
Vaginal pH > 5.5 hence alteration of bacterial flora +/- overgrowth e.g. Gardnerella vaginalis, Mycoplasma hominis, peptostreptococci, Mobiluncus and anaerobes e.g Bacteria species with too few lactobacilli (protective microbiota of female genitalia)
MICROSCOPY: Gram stained vaginal smear examined using Hay/Ison criteria:
GRADE 1: Normal - Lactobacillus morphocytes predominate
GRADE 2: Intermediate - Mixed flora, some Lactobacilli present but Gardenella or Mobiluncus morphocytes present
GRADE 3: BV - Mainly Gardenella +/- Mobiluncus morphocytes. Few or absent lactobacilli
What tests are used for Herpes Simplex Virus?
Direct Identification of Virus:
Direct staining, IMF, cell culture or PCR culture is GOLD STANDARD ( can distinguish HSV 1 & 2)
Culture is slow and costly (100% specificity)
PCR detects HSV DNA and is faster, more sensitive and less risk of contamination, compared with culture
IMF is less sensitive/specific than culture and is not recommended
Serology:
detects specific Ab (97% sensitivity, 98% specificity)
not used routinely - difficult to interpret significance of +ve result
What tests are used for HIV Serology?
Antibody tests:
EIA test (100% sensitivity) - no false negatives
All +ves confirmed using 1-2 other tests - Western blotting or EIA with higher specificity
Each lab has a testing algorithm
Always remember window period when interpreting results
Anitgen test: p24 antigen - useful in diagnosing 1ary infection as it is positive before Ab production
NAAT: Detect RNA
Quantitative tests - ‘viral load test’ - commonly used to monitor treatment
Can give false positives at low levels - not used for screening as not sensitive enough and also difficult, time consuming and costly
useful in diagnosing primary infection, as very high viral loads prior to Ab production
What tests are used for Hep A?
IgM AB: +ve in acute Hep A - start to appear 3-4 weeks following infection
IgG Ab: produced later on, used to detect past infection and indicates immunity
Lab tends to measure total Ab unless acute infection is suspected
What tests are used for Hep B?
Hep B Surface Antigen (HBsAg) - FIRST TO BECOME POSITIVE during infection, remains positive in chronic disease (HbsAg +ve > 6m)
IgM Hep B core antibody (anti-HBc): FIRST ANTIBODY detected shortly after HbsAg
IgG anti-HBc: signifies PREVIOUS INFECTION and is used to detect natural immunity
Hep B Surface Antibody (anti-HBs): The only Ab produced after vaccination as the vaccine contains surface Ag, used to check immunity following vaccination
Hep B e Antigen (HbeAg): presence of indicates high infectivity
What is the first thing to become during acute Hep B infection?
HbsAg
What is the first antibody to become positive in acute Hep B infection?
anti-Hbc
