By Tracey Shaw, MT(ASCP), and Jean Sapere, MT(ASCP)
Last year, our laboratory at Inland Hospital in Waterville, Me, began a quest to evaluate a new rapid test for C.difficile A/B after we noticed an increase in physician requests to test for both Toxin A and Toxin B. C.difficile disease is the result of the production of Toxin A, a tissue-damaging enterotoxin, and Toxin B, a potent cytotoxin. According to current reports from the Centers for Disease Control and Prevention, Maine is rated among the top six states in the country for C.difficile-associated disease. Our laboratory at Inland Hospital services a 48-bed inpatient, 4-unit emergency department, and general outpatient population.
Tracey Shaw works with a C.Difficile kit.
Sending out to our reference lab to test for Toxin B had a turnaround time of several days. In addition, it was sometimes difficult for us to assure physicians that the testing could be done. The specimen had to be less than 2 hours old and frozen before shipping. Hence, the request for an add-on C.difficile test did not always yield best practice for quality patient care because of specimen requirements and courier-pickup restrictions. It was apparent that we needed to provide education on the importance of this new test request for our emergency-department patients. Also, with new evidence that the organisms that are Toxin B positive can also cause disease, we were on the search for a reliable rapid assay that could perform both C.difficile A and B. Until recently, most of the rapid kits for C.difficile were capable of testing for and detecting Toxin A only. After reviewing current literature and information from the American Society for Microbiology, and talking with other colleagues in Maine, we decided this change needed to happen quickly.
We decided to test, concurrently, two new rapid C.difficile A/B test kits and to base our final decision on ease of use, ease of interpretation, testing time, sensitivity, specificity, pricing, and specimen requirements. While we were in the process of evaluating the new test kits, a patient arrived in our emergency department presenting with symptoms of C.difficile. The patient complained of abdominal pain with severe burning in the upper abdomen, nausea without vomiting, persistent mucous-tainted diarrhea, and loss of appetite. In addition, the patient had been prescribed an antibiotic for a nonrelated infection a few weeks earlier. Also, this patient was currently being treated for hypothyroidism. Upon arrival, the patients oral temperature was 98.4, pulse was 85, and blood pressure was 124/80. Current medications included levothyroxine 75 mcg per day, a weekly birth-control patch, and lansoprazole twice per day. Past surgeries included a breast augmentation, an umbilical hernia repair, a cesarean section, and a dilation and curettage.
Laboratory findings of the cbc, differential, and BMP revealed:
|CBC Results:||Chemistry Results|
|WBC: 12.0 Th/µL||Glucose: 95 mg/dL|
|Rbc: 4.44 mL/µL||Urea Nitrogen: 13 mg/dL|
|Hemoglobin: 14.5 g/dL||Creatinine: 0.9 mg/dL|
|Hematocrit: 42.9%||Sodium: 140 mmol/L|
|MCV: 96.6 fL||Potassium: 3.8 mmol/L|
|MCH: 32.7 pg||Chloride: 106 mmol/L|
|MCHC: 33.8 g/dL||CO2: 26 mmol/L|
|RDW-SD: 43.2 fL||Calcium: 9.4 mg/dL|
|Platelet: 277 Th/µL|
|Neutrophil %: 85.0||Absolute: 10.23 Th/µL|
|Lymphoctye %: 6.1||Absolute: 0.74 Th/µL|
|Monocyte %: 7.7||Absolute: 0.93 Th/µL|
|Eosinophil %: 1.0||Absolute: 0.12 Th/µL|
|Basophil %: 0.2||Absolute: 0.02 Th/µL|
A stool sample was submitted to the laboratory for culture and C.difficile. The stool culture offered by the laboratory included salmonella, shigella, shiga toxins, and campylobacter; all yielded negative results. The C.difficile offered at the time screened for Toxin A only, and was subsequently negative.
The specimen submitted was suspicious for C.difficile. We were currently evaluating the two kits capable of detecting Toxins A and B, so we ran the patient specimen on those kits as well. Results from both kits being evaluated were positive, suggesting that the culprit was C.difficile Toxin B. Since the new kits were still being evaluated, we made the emergency-department physician aware of these findings in a subsequent consultation. The decision was made to send the sample to another laboratory capable of detecting Toxins A and B to confirm our findings. The result of the send-out test was positive.
If we had not been in the process of evaluating the other kits, these results would have been unavailable for several days due to turnaround time. The patient was diagnosed with antibiotic-induced diarrhea by the emergency-department physician on the same day she was seen, and she was discharged with a prescription for Flagyl, a 250-mg oral tablet taken three times per day.
Antibiotic-associated diarrhea, caused by Clostridium Difficile, appears in only 15% to 25% of cases, but it can be a life-threatening complication of antibiotic use. Although the spore-forming, gram-positive anaerobic bacillus itself is not directly invasive, the individual or combined effects of Toxins A and B can cause bloody diarrhea with associated necrosis of the colon mucosa and pseudomembranous colitis. Typical symptoms also include cramping, abdominal pain, mucous green foul watery stools, fever, and leukocytosis. C.difficile is easily transmitted and is a frequent cause of hospital-acquired nosocomial diarrhea. Recent revelations that alcohol-based hand rubs and disinfectants may not be effective against spore transfer has led us back to the sinks to use soap and water and Environmental Protection Agency-registered hypochlorite-based (bleach) disinfectants.1
This emergency-department patient event helped to expedite our evaluation and further justified our decision to offer a rapid C.difficile test for Toxins A and B. It was a sure buy-in for our medical staff for efficient, quality patient care. The kit we chose, Meridian Immunocard, was easy to perform, easy to read, and took only 15 minutes to complete. It is a qualitative, horizontal-flow enzyme immunoassay. Although this is a sensitive assay, and it is used to help diagnose C.difficile-associated disease, we do still strongly suggest repeat testing in cases of high suspicion when the initial test is negative. Specimen-collection requirements are more versatile with this new methodology, which eliminated the previous problems we were encountering. Although the stool should be tested as soon as possible after collection, it may be held for up to 4 days at 2°C to 8ÞC and/or be frozen. Another plus is that since we no longer have to perform an extraction step, we now only have to run quality control once per box, as opposed to every day.
While there are new thoughts about testing for the antigen to screen out negatives and then performing cell-culture toxin studies on the antigen-positive samples2, smaller hospitals need to focus in on what is appropriate, affordable for them, and quick. With emergency-department patients waiting for results, rapid turnaround times are a must. This is where a bond is formed between manufacturers researching for better-marketable products, and laboratories looking for the best products at the best prices without compromising the best possible patient care.
Although laboratory technologists tend to be busy with patient testing, and managers are dealing with current operational events, this case study illustrates the absolute necessity to stay committed to education. Various media, including the Internet and clinical lab publications, have enabled laboratories around the world to evaluate and determine the directions we need to take with regard to new products and methodologies. For the sake of our patients, we need to stay abreast of ever-changing current events to win in the game of disease versus patient.
Tracey Shaw, MT(ASCP), is microbiology supervisor, and Jean Sapere, MT(ASCP), is laboratory director, Inland Hospital, Waterville, Me.
1. C.difficile fact sheet. Available at: http://www.cdc.gov/ncidod/hip. Accessed September 9, 2005.
2. Fedorko DP. Controversies in Clostridium Difficile Testing. Clinical Microbiology Newsletter. 2002;24:7679.