What is nitrite testing?

Nitrite testing is a chemical test used in urine testing to detect nitrites (nitrituria).¹

Nitrites are not usually present in urine, a positive test could suggest a urinary tract infection (the urinary tract includes the urethra, bladder, ureters and kidney).²

Nitrite formation

Urine contains nitrates, when bacteria are present, they convert nitrate into nitrites using an enzyme.³

A positive nitrite urine test may suggest a large number of bacteria in the urine.² 

Conditions associated with nitrite positive urine

Asymptomatic bacteriuria (ASB)

•  Bacteria is present in the urine but you have no symptoms⁴

Symptomatic urinary tract infection (UTI)

• Anyone can have a UTI
• Women (persons assigned female at birth) are more likely to develop UTI’s as the anatomic distance between the urethra (a tube used for urination) and anus is shorter so bacteria travel easier 
• 20% of patients still experience UTI symptoms despite having a negative bacterial culture⁴

Risk factors for UTI

• Women (persons assigned female at birth)
• Sexually active
• Having a new sexual partner
• Using spermicides (a type of birth control placed in the vagina)
• Previous UTI
• Older adult or young child
• Experiencing menopause
• Pregnant
• Diabetes
• Immunocompromised persons
• Known structural abnormalities in the urinary tract
• Recent surgery
• History of UTI in a female first-degree relative (this increases your chance of recurrent UTIs)
• There is an increased risk of acute pyelonephritis (kidney infection) occurring in families of children who have had the illness^4,5,6,7

Uncomplicated UTI/cystitis

Uncomplicated UTI/cystitis is the most common (bladder or urinary tract infection).⁴ 

You may have an uncomplicated urinary tract infection if all the following apply to you:⁴ 

• You are female
• Not pregnant
• Not immunocompromised
• Have no known functional or anatomical abnormalities in your urogenital tract (this includes your reproductive system which consists of your vagina, womb and urinary tract)
• No signs of bacteria invading tissues or systemic symptoms (symptoms that affect the entire body see urosepsis symptoms)
• Have Uncomplicated UTI symptoms(see symptoms of uncomplicated UTI)

Some bacteria that cause UTI’s are:⁸

• E. coli 
• Klebsiella pneumoniae
• Enterococcus faecalis
• Proteus mirabilis

Uncomplicated UTI symptoms:

• Pain with urination with or without feeling the need to urinate frequently
• Feeling that you need to urinate urgently often
• Feeling the need to urinate more during the night (nocturia)
• Feeling pain in the bladder
• Hematuria (blood in your urine)
• Pungent urine
• Cloudy urine
• Fever^2,4,9

Recurrent UTI is defined as aUTI that has occured 3x in the last year or more or 2x in the last 6 months. This happens to 20-30% of women (persons assigned female at birth).^4,10

Acute pyelonephritis is described as infection of the kidney and tubes connecting the bladder and kidneys.

Symptoms:

• Fever (temperature of over 38°C)
• Chills
• Mental confusion
• Flank pain
• Nausea or vomiting
• Pain with urination with or without feeling the need to urinate frequently
• Feeling that you need to urinate urgently often
• Hematuria (blood in your urine)^4,11

Bacterial prostatitis

An inflamed/swollen prostate due to a bacterial infection.

Symptoms:

• Fever 
• Feeling the need to urinate frequently
• Pain with urination with or without feeling the need to urinate frequently
• Cloudy urine
• Pain between the anus and scrotum, or pain at the tip of the penis which may radiate to the abdomen, lower back or rectum
• Painful ejaculation
• Difficulty urinating
• General unwellness
• Muscle aches and pains¹²

Urosepsis 

A life-threatening reaction to an infection originating in the urinary tract, bladder or kidney.^1,3,14

Symptoms:

• Fever 
• Fast heart rate 
• Difficulty breathing
• Decreased urine output
• Pain with urination with or without feeling the need to urinate frequently
• Flank pain (tummy pain just below ribs)
• Difficulty urinating
• Hematuria (blood in your urine)
• Vomiting^13,14

The NHS⁹ reports that a child with a UTI may present with:

• Fever 
• General illness
• Irritability
• Loss of appetite 
• Vomiting
• Wet themselves

The NHS notes that people with a catheter, frail and old people with a UTI may:

• Shake or shiver
• Show behavioural changes, such as being confused or agitated
• Wet themselves, more/worse than usual

Diagnostic methods

Nitrite testing:

• Performed by dipping a rapid urine test strip into a urine sample
• Will indicate if your urine contains nitrite or not
• Can be purchased over the counter or can be performed by your GP 
• Most rapid urine tests have tests for leukocyte esterase (a substance suggesting the presence of white blood cells) and blood which is also an infection indicator
• Do not use this test to rule out or confirm infection^1,2,15

Uncomplicated UTI/cystitis diagnosis:

• Your GP will use your symptoms and rapid urine tests to confirm or rule out a UTI or other infection and may ask questions about your symptoms¹⁶ 
• Your urine may be cultured (grown) in the lab^17,18

This is the best way to detect an infection and will provide information on the type of bacteria and best antibiotic treatment.

Acute pyelonephritis diagnosis:

• Urinalysis
• Urine culture
• Blood tests To evaluate kidney function¹⁹

Bacterial prostatitis diagnosis:

• Test for sexually transmitted infection
• Urinalysis 
• Abdominal exam 
• Rectal exam An exam of the scrotal area¹²

Urosepsis diagnosis:

• Urinalysis
• Urine culture
• Blood tests(to check for infection, inflammation and organ function)
• Ultrasonography (this is to check for obstructions)²⁰

Limitations and considerations

False positive:

• If dipsticks have been exposed to the air for too long
• A bacterial species that does not convert nitrite to nitrate (especially with complex UTI)^2,3

False negative:

• Elevated specific gravity (a measure of how concentrated urine is)
• Increased urobilinogen (may be increased if you have liver problems)
• high levels of vitamin C²

Sensitivity and specificity:

• Only 25% of patients with a UTI get a positive nitrite test
• 94-100% of patients who test positive for nitrite have a UTI³

Clinical management

The NHS advises that you can see a pharmacist about your UTI/cystitis, however you must see a GP if:

• This is your first UTI
• You are amale (person assigned male at birth)
• You are pregnant 
• You are caring for a child who has UTI symptoms
• Using a urinary catheter
• Are an older person
• Have UTI symptoms following surgery
• You aren't feeling better or are feeling worse after 2 days

The NHS advises that you see a GP urgently or ring NHS 111 if:

• You are feeling drowsy or disoriented
• Your urine has blood in it 
• You experience chills or have a fever
• You have a low temperature
• Feel pain in your tummy just below your ribs

Treatment 

Uncomplicated UTI:

• A short course of antibiotics, though this isn’t always needed^{9,21,22,23,24}
• Usually 100mg Nitrofurantoin for 3 days or Trimethoprim (200mg) for 3 days
• Painkillers such as paracetamol
• Drinking lots of water
• People do take cranberry products or cystitis sachets as a treatment, though there is no evidence to say that this is beneficial once you have an infection

Bacterial prostatitis

Acute(sudden onset) symptoms:

• Painkillers
• 2-4 weeks of antibiotics²⁵

Chronic symptoms (come and go over several months):

• Painkillers and anti-inflammatories (e.g. ibuprofen and paracetamol)
• Antibiotics
• Alpha blockers - muscle relaxant for the base of the bladder and prostate
• Laxatives if defecating is painful²⁵
• If there is an abscess it will need to be drained

Acute pyelonephritis:

• A course of antibiotics
• People tend to feel completely better within 2 weeks²⁶

Urosepsis:

• Antibiotics through an IV line
• IV fluids (to prevent a drop in blood pressure)
• Supplemental oxygen may be given through nasal cannula or face mask²⁷ 

Prevention strategies

Hygiene practices:

• Make sure the genital area is clean
• When you go to the toilet, always make sure to wipe from front to back
• Change soiled incontinence pads and nappies as soon as possible
• Urinate as soon as you can after sexual intercourse
• Use water to clean the vagina both before and after sex
• Keep hydrated
• Urinate regularly
• Take showers, not baths, to wash away soaps
• Don't use spermicidal lubrication
• Avoid scented soap
• Avoid sugary foods
• Avoid alcohol
• Don’t wear synthetic and/or tight-fitting underwear^9,21

Medication

ALWAYS talk to your doctor before trying any new medication.!

Antibiotic prophylaxis:

• Antibiotics for 6-12 months
• Antibiotics after having sex²⁸

Both options are effective in preventing UTI.

Non antibiotic prevention:

• Vaginal oestrogen in postmenopausal women
  • Shown to be effective at preventing UTI²⁹
• May prevent UTI’s but evidence is limited:
  • Cranberry Juice and D-mannose^30,31
  • Methenamine hippurate³²

Summary

• Nitrite test strips can be used to detect nitrite in the urine
• Nitrite in the urine may be a sign of a urinary tract infection
• You should make an appointment with your GP if you experience a burning sensation when you urinate or notice cloudy or pungent-smelling urine
• GP’s use symptoms, lab tests and physical exams to determine the type of UTI
• Treatment of a UTI depends on whether it is complicated or uncomplicated, but mainly involves antibiotics
• Behavioural modifications, prophylactic antibiotics, vaginal oestrogen and other remedies may help to prevent UTI