The difference between urine routine and urine culture

Urinalysis is to check whether the content of various components in urine exceeds the standard. This test is usually affected by many factors, so it is not very accurate as a basis for diagnosis and can only be used as a reference. Urine culture is to check whether there are bacteria in the urine. If there are bacteria, the bacteria in the urine must be cultured to analyze whether the characteristics of the small bacteria are pathogenic. This culture can be used to determine whether the urinary system is normal.

Differences between urinalysis and urine culture

Urinalysis is the most basic test, such as the presence of white blood cells, red blood cells, protein, nitrates, etc., while culture is for bacteria to check for sensitive bacteria.

What is urine culture

Urine culture refers to the growth of bacteria in normal urine. Normal urine should be a sterile liquid, but there are various bacteria on the surface of the human urogenital tract. Since the pH in the female vagina is acidic, there are generally no pathogenic bacteria, but there are many conditional pathogens such as lactobacilli. As the pH changes, the normal flora will also change. Therefore, urine culture should be performed in a sterile manner (it is best to clean and disinfect the external urethra under the guidance of a doctor) to eliminate interference from external bacteria and accurately detect whether there are bacteria in the urine, whether they are pathogenic bacteria or conditional pathogens.

Factors affecting urine routine examination

(1) Urine should be collected fresh and should not be left for more than 1 hour, otherwise the bacteria will increase and a false positive will occur.

(2) The urine stays in the bladder for a short time (less than 6 hours) or the patient drinks too much water, which dilutes the bacteria in the urine and affects the accuracy of the results.

(3) The midstream urine collection is not up to standard. Vulvar disinfection has a great impact on urine culture. Too much disinfectant is mixed into the urine specimen, inhibiting bacterial growth and resulting in a false negative result.

(4) If antibiotics were used before urine culture, a false negative result may occur.

(5) Bacterial excretion in urinary tract infection may be intermittent. For example, when chronic pyelonephritis has no acute symptoms, urine culture may be negative, but during its acute attack, urine culture is often positive.

(6) Errors in vaccination technique may also affect the results.

(7) In cases of hematogenous acute pyelonephritis, small abscesses are formed in the renal parenchyma, and the mucosal lesions of chronic pyelonephritis tend to heal, but the renal parenchymal lesions still exist; or in cases of urinary tract obstruction with coexisting infection foci and urinary tract obstruction, the bacteria in the urine are often negative.

(8) Different bacterial species have an impact on colony counts.

Clinical significance of urine culture

If any of the bacteria such as Staphylococcus, Escherichia coli, diphtheroids, yeasts and Lactobacillus (female) are found in urine culture, it will cause urinary tract infection. Therefore, the significance of urine culture test is to monitor whether the human urinary system (including kidneys, bladder, and urethra) is healthy and sterile. If there is a bacterial infection, an antibiotic sensitivity test for the bacteria should be performed to guide the doctor to use antibiotics accurately and in the right amount to kill the bacteria as soon as possible.