Table 2.

The Effect of Various Testing Algorithms on Isolation of Patients with CDI

Testing approach	Average cost/test ($)	Sensitivity of test/algorithm (%)⁎	No. of patients positive for CDI missed	Specificity of test/algorithm (%)⁎	No. of false-positive test results	Patients in isolation with CDI	Patients in isolation without CDI	Patients with CDI not in isolation
GDH or EIA alone	18.00	55	45	94	54	Days 1–5, 55	Days 1–5, 54	Days 1–5, 45
Reflex to NAAT for GDH+ and EIA-	19.12	85	15	93.9	55	Day 1, 55; days 2–5, 85	Day 1, 54; days 2–5, 55	Day 1, 45; days 2–5, 15
Reflex to toxigenic culture for GDH+ and EIA-	18.51	86	14	93.9	55	Days 1–4, 55; day 5, 86	Days 1–4, 54; day 5, 55	Days 1–4, 45; day 5, 14
Reflex to direct cytotoxin for GDH+ and EIA-	18.32	77	23	93.9	55	Days 1–2, 55; days 3–5, 77	Days 1–2, 54; days 3–5, 55	Days 1–2, 45; days 3–5, 23
NAAT alone	35.00	95	5	96	36	Days 1–5, 95	Days 1–5, 36	Days 1–5, 5

Assumptions: 1000 patients tested with each test or algorithm; 10% prevalence (ie, 100 true-positive patients and 900 true-negative patients); GDH-positive and EIA-negative samples = 32, which will be retested using one of the reflex methods; testing on first shift of each day; one test type is performed per day; no pre-emptive isolation if test results are reported on same day as ordered (ie, <8-hour turnaround time); pre-emptive isolation for CDI orders includes time for other tests; isolation continues until the day the test result is negative; assumes a 5-day length of stay.

^⁎Sensitivity and specificity values are based on published literature.^{2–5,7–10,26–30,32–37,44–48,53–56,58–61}