Diary of the “mad” med-lab techs

Urine cultures are a real bug-a-boo (pun
intended) for both the sending and the testing laboratory.
Having been on both ends of the sample trail, I can say that
neither sender nor recipient have a monopoly on “doing it
right.” In order to keep from setting up micro in our small
hospital, and with 85% of our culture requests for urines, we
used the small urine culture “fat tubes with media” (I cannot
remember what the actual brand was) to set up fresh specimens.
If anything grew, there was a one-day or two-day's growth head
start when the samples went to the reference lab for
confirmation. We could also report out the 75% or more “no
growth” or “mixed flora” samples — saving time and money.

—By Chuck Millstein, MBA,
MT(ASCP), CLDir(NCA), gratefully retired

Urine specimens have got to be one of the
hardest cultures to sort out. There are so many variables that
make it nearly impossible to set etched-in-stone standards for
all specimens, regardless of all the complicated algorithms
available. Although the majority of outpatient urinary-tract
infections are caused by a few common bacteria and are easily
identified, the real problem lies in the not-so-simple cultures
(e.g., inpatients, extended-care facilities, post-surgical
manipulation, patients on long-term antibiotics, patients with
indwelling catheters, infants and small children, and patients
with underlying disease).

Stop with the office dipstick! Office
dipstickers send us urine for culture based on their
interpretation and provide us with very little information. With
the advent of computers, we are able to view the patient's
urinalysis report for clues to the importance of the organisms
grown in culture. If there is no urinalysis information, we are
handicapped; so what we report may not be accurate. If you must
dipstick to screen out normal urines, at least order a complete
urinalysis and culture for those you interpret as “positive” by
dipstick. Many laboratories will not culture a urine without an
order for a urinalysis.

• Be careful what you report.
  Preliminary reporting may lead to misinformation and
  unnecessary antibiotic therapy. Example: After 18 to 24
  hours incubation, 40,000 col/mL of big shiny Group B
  Streptococcus are reported on a non-pregnant patient. The
  provider sees this as a pure culture and acts on it. After
  an additional 24 hours' incubation, the culture also grows
  out >100,000 col/mL of mixed skin/vaginal flora. Now you
  change the report to “mixed skin/vaginal contaminants.”
• Anaerobic urinary-tract
  infections. Are they being missed? You bet they
  are. Until we can configure our automated information system
  to flash the urinalysis result on the screen when we call up
  the culture — not just the dipstick results but the
  microscopic — we will continue to report out “no growth”
  results where, in fact, the bacterial culprit is fastidious
  or anaerobic.
• Good practice. A
  provider calls up and asks you to explain why his patient's
  culture report was “no growth,” but the urinalysis indicated
  an infection. Repeating the culture will more than likely
  produce the same results. Pull the saved urine aliquot from
  the refrigerator; place several drops on a glass slide;
  air-dry, methanol-fix, and Gram stain. If you see no
  organisms in several oil-immersion fields, report your
  Gram-stain results and go no further. If you see bacteria in
  the Gram stain, repeat the culture using additional enriched
  aerobic and anaerobic media.
• Save a sample. Save
  aliquots of all urines that come into your lab and
  refrigerate for at least 72 hours. We did an unpublished
  study on the viability of urines cultured at increasing
  lengths of time after refrigerated storage. We cultured them
  initially, again at 24 hours, 48 hours, 72 hours, and 96
  hours. There was virtually no change in recovery of the
  pathogen and colony count in the 72-hour refrigerated sample
  from results of the initial culture and only a small drop in
  colony count at the 96-hour sample. The majority of the
  organisms that dropped off in recovery rates were generally
  the microaerophilic skin/vaginal contaminants. Many times a
  patient will present in the emergency department with a
  raging urinary-tract infection diagnosed by urinalysis and
  suspected urosepsis. The patient is admitted and
  administered IV antibiotics, and the provider waits for the
  culture results. After two days, the patient does not seem
  to be improving, and his blood cultures remain negative. The
  provider calls the lab and finds out that a urine culture
  was never ordered. Are you going to tell the provider that
  the urine was not saved, or that you cannot use the urine
  because it is more than 24 hours or 48 hours old? The
  patient has been on antibiotics, so a new sample probably
  will not be useful. Use common sense and provide for the
  good of the patient.

Two additional cautions:

1. Just because the specimen is labeled
catheterized does not mean that what grows out is always
important. Again, look at the urinalysis. In-out catheterized
samples could be misleading in that the catheter may have pushed
an abundance of normal distal urethra or vaginal flora into the
bladder, which is then recaptured in the sample.

2. A study was done to assess the
difference between clean-void midstream (CVMS) and voided urine
samples. At the conclusion of the study, it was found that there
were more contaminants in the CVMS samples then the voided ones.

Think outside the proverbial box. There
are so many variables in the processing and reporting of urine
cultures. The higher the number of cultures you have to process
does not have to mean you have to get a lower level of accuracy.