Table 1.

Validity of single quarter samples in diagnosing intramammary Staph. aureus infections (95% confidence interval between brackets)

	All cows	Cows with SCC > 200,000 cells/ml	Cows with SCC repeatedly >200,000 cells/ml
Sensitivity	0.92 (0.90; 0.95)	0.91 (0.88; 0.95)	0.90 (0.86; 0.95)
Specificity	0.98 (0.98; 0.98)	0.87 (0.86; 0.89)	0.97 (0.97; 0.98)
Pred. Value Pos.	0.54 (0.51; 0.58)	0.41 (0.38; 0.46)	0.82 (0.78; 0.88)
Pred. Value Neg.	0.99 (0.99; 1.00)	0.99 (0.99; 0.99)	0.98 (0.98; 0.99)