Drew and Boyle developed the RUWA (ratio, urea, WBC, albumin) scoring system for evaluating a patient with Clostridium difficile colitis. The authors are from St. James's Hospital in Dublin.
Parameters:
(1) ratio of the white blood cell count on the day of first positive C. difficile toxin test to the white blood cell count 2 days previously
(2) urea in mmol/L on the day of the positive toxin test
(3) white blood cell count on the day of the positive toxin test
(4) serum albumin in g/L on the day of the positive toxin test
Parameter
Finding
Points
WBC ratio
0 to 0.49
1
0.50 to 1.50
0
1.51 to 2.00
1
2.01 to 4.00
2
> 4.00
3
urea
< 10 mmol/L
0
10 to 20 mmol/L
1
> 20 mmol/L
2
white blood cell count
< 4 * 10^9/L
1
4 to 10 * 10^9/L
0
10.1 to 20 * 10^9/L
1
20.1 to 30 * 10^9/L
2
> 30 * 10^9/L
3
serum albumin
> 30 g/L
0
24 to 30 g/L
1
< 24 g/L
2
where:
• Patients were in an enhanced surveillance program so toxin testing was done promptly in a person with a compatible clinical picture.
total score =
= SUM(points for all 4 parameters)
Interpretation:
• minimum score: 0
• maximum score: 10
• A score >= 4 is associated with risk of severe complications.
Performance:
• The sensitivity was 80% and specificity 77% on day 1 of active surveillance.
• The sensitivity was 63% and specificity 82% on day 3 of active surveillance.
• If a person is evaluated on days 1 and 3, the sensitivity was 100% and specificity 70%.
• The negative predictive value was high so a person identified as low risk is unlikely to have serious complications.
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