A reader posted on my CFSRemission facebook page:
- [Background] “Calprotectin is a heterodimeric protein which belongs to the calcium-binding protein S100 family. Calprotectin is released by leukocytes at the site of inflammation and it can be detected in the feces where it remains stable for about a week. Hence, increased fecal calprotectin (FC) levels are found in several inflammatory conditions, mainly the inflammatory bowel diseases (IBD).”
- ” the calprotectin levels in 86% of paediatric faecal samples and 95% of samples from adults correlated with the endoscopic evidence, reflecting the high sensitivity of the test in all age groups…. controversy remains regarding the predictive value of faecal calprotectin in patients in remission…. may also help to spare patients from unnecessary endoscopy when calprotectin levels are low. ”  – so 5% chance of false negative.
- “With several faecal calprotectin (FC) assays on the market, it has been difficult to define a uniform threshold for discriminating between remission and active disease in patients with inflammatory bowel disease (IBD). We aimed to compare the results of different FC-assays in IBD patients, followed over time…. Cross-comparisons revealed overall poor agreement between the assays as well as differences in the dynamics of FC. These findings suggest that standardisation of the method is needed to implement FC as a disease monitoring tool at large-scale.” 
CFS and Microbiome
CFS and IBS are co-morbid. To be more accurate 16% of CFS has IBS while 5% of non-CFS patients have IBS. So a CFS diagnosis does not mean that you have IBS — the odds are 3.3 time greater that you have IBS if you have CFS.  In fact, it is almost a toss up of which came first for patients that have both: CFS before or at same time as IBS – 50%, CFS after IBS – 50%. 
I could only find a single study on calprotectin and CFS.
- “The faecal calprotectin levels were normal in all patients (< 50 mg/kg faeces) although 3 patients had occasionally higher values (one sample per patient on days 14, 42 and 70 respectively).”  There were 15 patients in the study so 3/15 = 20% had occasionally higher values (and above we had a report of 16% with IBS) so we have agreement between the studies.
As a CFS diagnostic tool, faecal calprotectin is of no apparent use (for IBS, that is not the case).
Given faecal calprotectin and IBS association, I looked at probiotics results for this specific measure. NOTE: some of these studies were on infants — uncertain if they apply to adults.
- NONE: Lactobacillus plantarum 299 and Bifidobacterium infantis Cure 21 
- NONE: Bacillus coagulans GBI-30, 6086 (BC30); GanedenBC(30)  – inferred
- NONE: Lactobacillus rhamnosus HN001 and Lactobacillus acidophilus NCFM 
- NONE: Lactobacillus acidophilus (L. acidophilus) NCFMTM (ATCC 700396) and Bifidobacterium lactis (B. lactis) Bl-04 (ATCC SD5219)” Neither the probiotic treatment, nor pollen season had any significant effects on the fecal calprotectin concentrations.” 
- NONE/Little: lactobacilli (La-5) and bifidobacteria (Bb-12) “Calprotectin levels did not change significantly after intervention. “
- Improved: Bifidobacterium breve PS12929 and Lactobacillus salivarius PS12934. 
- ” detected as high fecal calprotectin, predicted asthma and AD by the age of 6 years and was linked to low abundance of fecal Escherichia“
- Improved: Lactobacillus reuteri 
- Improved: mixture of Lactobacillus casei, Lactobacillus rhamnosus, Streptococcus thermophilus, Bifidobacterium breve, Lactobacillus acidophilus, Bifidobacterium infantis (child-specific), Lactobacillus bulgaricus 
- Improved: Bifidobacterium lactis Bb12 
- Improved: Lactobacillus GG 
- WORST: Lactobacillus reuteri DSM 17938 “The probiotic-treated group had a significantly higher fecal calprotectin level than the placebo group after 2 months of treatment” 
For IBS with high Calprotectin levels, the studies suggest the following probiotics:
- E.Coli probiotics (Mutaflor, Symbioflor-2)
- Lactobacillus GG
- Bifidobacterium breve PS12929 and Lactobacillus salivarius PS12934
- Bifidobacterium lactis Bb12