Spinal fluid samples are either clear or turbid. Some sources use the following rating system for turbid CSF specimens:
- 0 = crystal clear fluid
- 1+ = faintly cloudy, smoky, or hazy
- 2+ = turbidity clearly visible but newsprint read easily through tube
- 3+ = newsprint not easily read through tube
- 4+ = newsprint cannot be seen through the tube
Turbidity may be caused by white blood cells (WBCs), red blood cells (RBCs), fungi, bacteria, amoebae, contrast media, or aspiration of epidural fat during puncture.
200 WBCs/mm3 will cause slight turbidity (1+); increased numbers of WBCs will cause increased turbidity. At least 400 erythrocytes/mm3 are needed to produce 1+ turbidity
CSF may have an oily appearance due to the presence of substances remaining in the fluid following radiologic (x-ray) procedures.