Table 3.

Positive and negative predictive values for having a large syrinx (≥ 4 mm)

Clinical sign	PPV	NPV
Unprovoked scratching Q2
- Yes/No - Often-Always/ Sometimes-Never	0.71 0.77	0.75 0.63
Scratching neck or shoulder Q3	0.74	0.69
Unilateral scratching Q4 in dogs scratching the neck or shoulder	0.72	-
Bilateral scratching Q4 in dogs scratching the neck or shoulder	0.80	-
Phantom scratching Q5	0.74	0.58
Aggravation of scratching during emotional arousal Q6	0.74	0.59
Aversion to touch on head, neck or shoulder Q7	0.74	0.58
A preferred head posture during sleep Q13	0.82	0.52

NPV: negative predictive value; PPV: positive predictive value; Q: question number referring to the questionnaire; SM: syringomyelia