🤔 MEDIUM

Eight questions to test your understanding of the diagnosis, investigations and medical management of sexually transmitted infections, genital discharge and genital ulcers. For questions specifically about HIV see here and here.

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STIs

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Question 1
A 24 year old male patient visits his GP complaining of pain in his left knee. On further questioning he also describes a burning sensation on urination and he has noticeable conjuctival inflammation. He denies any recent gastroenteritis but  has had several sexual partners and has not always used protection. Given the most likely diagnosis, which bacteria is most likely responsible?
A
Neisseria gonorrhoea
B
Chlamydia trachomatis
C
Treponema pallidum
D
Trichomalis vaginalis
E
Mycoplasma genitalium
Question 1 Explanation: 
The stem describes the triad of dysuria, arthritis and uveitis that is a classical presentation of reactive arthritis. The triad is also known as Reiter's syndrome. It most commonly follows a chlamydia or gastrointestinal infection and is caused by Gram negative organisms.

BMJ Best Practice describes several other symptoms and risk factors - the classic triad of symptoms can be misleading.

Question 2
What is the most appropriate treatment for chlamydia for an adult who is not pregnant?
A
Aciclovir
B
Azithromycin
C
Benzylpenicillin
D
Ceftriaxone
E
Doxycycline
Question 2 Explanation: 
Doxycycline is the treatment of choice, although azithromycin is recommended if the bacteria is shown to be sensitive or in pregnancy. See NICE CKS. Sexual partners will also need treatment, the patient should be counselled on the use of effective contraception, and should be told to refrain from sexual intercourse and oral sex until they have completed their course of doxycycline (or 7 days after starting azithromycin). They should also be screened for other STIs.
Question 3
Which investigation in the first line diagnostic investigation for gonorrhoea and chlamydia?
A
Dark ground microscopy
B
MC&S
C
NAAT
D
Serology
E
TPHA
Question 3 Explanation: 
MC&S may be useful in confirming the sensitivity to certain antibiotics but is not used for diagnosis. TPHA and dark ground microscopy are methods of diagnosis syphilis.
Question 4
What is the sample of choice for NAAT testing for uncomplicated chlamydia in a female?
A
Blood sample
B
First-catch specimen of urine
C
High vaginal charcoal swab
D
Mid-stream specimen of urine
E
Vulvo-vaginal swab
Question 4 Explanation: 
According to NICE, the vulvo-vaginal swab is preferred method of collecting the sample, although a first-catch specimen can also be used. First-catch urine is used for men.
Question 5
A male visits the sexual health clinic with a single, painless ulcer on the shaft of his penis. He denies any other symptoms. He admits to several sexual partners over the course of the last three months, and does not remember if he wore a condom on all occasions. He has no known drug allergies. Given the most likely diagnosis, what is the treatment of choice?
A
Aciclovir
B
Azithromycin
C
Benzylpenicillin
D
Corticosteroids
E
Doxycycline
Question 5 Explanation: 
A painless ulcer is most likely to be caused by syphilis. Aciclovir is the treatment for genital herpes, and strong corticosteroids can be used to treat Behcet's disease, a non-sexually transmitted inflammatory condition. These latter two conditions would present with painful ulcers.
Question 6
A 33 year old women attends her GP with a three day history of a white, fishy vaginal discharge. She has a long term sexual partner and no history of sexually transmitted disease. She has no dysuria and is afebrile. No blood is present in the discharge and she has no post-coital bleeding. On speculum examination, there is a milky fluid in the posterior fornix but no signs on inflammation. What is the most likely diagnosis?
A
Bacterial vaginosis
B
Candidiasis
C
Chlamydia
D
Donovanosis
E
Gonorrhoea
Question 6 Explanation: 
According to NICE, bacterial vaginosis is the most common cause of vaginal discharge in women of child-bearing age. Candidiasis (thrush) could also cause these symptoms but would more likely be pruritic (itchy) and would not have a fishy smell. Note: candidiasis and bacterial vaginosis are NOT sexually transmitted infections.
Question 7
What is the most appropriate treatment for the above condition?
A
Azithromycin
B
Ceftriaxone
C
Clindamycin
D
Doxycycline
E
Metronidazole
Question 7 Explanation: 
Metronidazole is ideally given orally, but can be offered topically. Clindamycin is an appropriate alternative.
Question 8
A 30 year old woman presents to her GP with dysuria and vulvodynia. On examination, the GP finds clusters of vesicles on the vulva and in the vagina. The doctor suspects HSV infection. The GP takes a swab. What is the investigation of choice to confirm the diagnosis?
A
MC&S
B
p24 antigen test
C
PCR
D
Serology
E
VDRL test
Question 8 Explanation: 
HSV is a virus so MC&S would not find anything. The p24 antigen test looks for HIV infection. Serology can be used to determine if this a patient's first infection. A VDRL test is a test for syphilis. Note that all patients with an STI should be screened for other STIs.
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