As a matter of review the CEAP system is based on Clinical findings(usually on physical examination), Etiology(congenital, primary, or seconday), Anotomic findings(superficial, deep, or perforating veins), and Pathophysiology(reflux or obstruction).
It is quite common for patients to have only spider veins(C-1), but have significant underlying venous reflux that can be diagnosed by history( pain, heaviness, restless legs, itching, throbbing, etc.), and, most accurately, by diagnostic duplex ultrasonography.
In our clinical practice as phlebologists we often see patients who lack varicosities (C2), edema (C3), or skin changes (C4), BUT have significant symptoms due to their underlying superficial venous reflux, which we can diagnose and treat in our clinics.
Although there has been no specific figure published, a significant percentage of patients who only have spider veins on clinical exam have advanced symptoms and abnormal duplex ultrasound, consistent with clinically significant superficial venous insufficiency. It is important to remember that symptoms of superficial venous reflux often develop BEFORE the patient progresses to C2 and beyond in their clinical presentation.