containing 0 01 to 1 w v based on the total volume of the buffer of at least one protein such as albumin or gelatin and having a ph of from 4 to 8 5 a preferred reaction temperature is from 2 u00b0 to 40 u00b0 c the reaction time is an important factor affecting on determination sensitivity and with operating convenience being taken into consideration preferably ranges from 10 minutes to 4 days then labelled human tenascin or a labelled anti human tenascin antibody is added thereto to further allow the system to react preferred reaction temperature and time are the same as in the above reaction i e at 2 u00b0 to 40 u00b0 c for 10 minutes to 4 days after the reaction the water insoluble carrier is washed with water or an appropriate buffer and the labeling substance bound to the water insoluble carrier is determined the above mentioned series of operation are conducted using a standard preparation containing a known concentration of human tenascin and the measured value of the cerebrospinal fluid is compared with that of the standard preparation to obtain the tenascin level in the cerebrospinal fluid sample a procedure of the foregoing assay in the case of use of serum as a sample is described in detail e g in biomedical research vol 14 no 3 pp 203 208.