A logistic, multiple regression model using 4 variables was developed to distinguish acute bacterial from acute viral meningitis.
Variables:
(1) age of patient: The risk of bacterial meningitis rises from 1 month to 1 year of age, followed by a sharp drop from 1 to 2 years, with a gradual decline to age 22, after which there is a gradual increase through adult life into old age.
(2) month of the year. Viral meningitis tends to occur in mid-summer; bacterial meningitis occurs year round but is relatively more common in the winter.
(3) ratio of glucose in CSF to blood
(4) CSF PMN count (CSF WBC count times percent PMNs in CSF differential)
probability of acute bacterial meningitis =
= 1 / (1 + (EXP (-L)))
L =
= (age factor) + (month from August 1st factor) + (glucose ratio factor) + (CSF PMN count factor)
|
Factor |
Finding |
Value |
|
age |
<= 1 year |
(2.29 * (age)) + 2.79 |
|
|
> 1 AND <= 2 |
((-2.71) * (age)) + 7.79 |
|
|
> 2 AND <= 22 |
((-0.159) * (age)) + 2.69 |
|
|
> 22 |
(0.100 * (age)) - 3.01 |
|
month from August 1st |
January |
0.52 * (4.97 + ((day of month) / 31)) |
|
|
February |
0.52 * (6.03 - ((day of month) / 29)) |
|
|
March |
0.52 * (5.03 - ((day of month) / 31)) |
|
|
April |
0.52 * (4.03 - ((day of month) / 30)) |
|
|
May |
0.52 * (3.03 - ((day of month) / 31)) |
|
|
June |
0.52 * (2.03 - ((day of month) / 30)) |
|
|
July |
0.52 * (1.03 - ((day of month) / 31)) |
|
|
August |
0.52 * (((day of month) / 31) - (0.03)) |
|
|
September |
0.52 * (0.97+ ((day of month) / 30)) |
|
|
October |
0.52 * (1.97+ ((day of month) / 31)) |
|
|
November |
0.52 * (2.97+ ((day of month) / 30)) |
|
|
December |
0.52 * (3.97 + ((day of month) / 31)) |
|
glucose ratio |
(CSF-to-blood glucose ratio) < 0.6 |
-12.76 * (ratio) |
|
|
(CSF-to-blood glucose ratio) >= 0.6 |
-12.76 * (0.6) |
|
CSF PMN count |
|
0.341 * ((CSF PMN count in 10^6/L) ^ (0.333)) |
CSF-to-plasma glucose ratio =
= ((CSF glucose in mmol/L) + 0.1) / ((blood glucose in mmol/L) + 0.1)
If a Gram-stain on the CSF was positive, the probability was set to 0.99.
Specialty: Infectious Diseases, Neurology
