This test is used to assess kidney function. For more info, check out http://labtestsonline.org/understanding/analytes/gfr/glance.html
Since your eGFR is very close to the normal range, the doctor may not have considered the result to be significant in your case - especially if you have normal creatinine level and no symptoms of kidney damage.
Chronic Lyme Disease, Gluten & Sulfite Sensitivity, Many Food/Inhalant/Medication/Chemical Allergies & Intolerances, Asthma, Gut issues (dysmotility, non-specific inflammation), UCTD ("Secondary Lupus-Like Syndrome"), Osteoporosis, Pancytopenia, chronic malabsorption/malnutrition, etc.; G-Tube; Currently TPN-dependent.
Meds: Zofran, Pulmicort, Heparin (to flush PICC line), IV Ceftazidime (for Pleural Effusion), Colloidal Silver (used topically).