In 2006, the ESSIC society proposed more rigorous and demanding diagnostic methods with specific classification criteria so that it cannot be confused with other, similar conditions. Specifically, they require that a person must have pain associated with the bladder, accompanied by one other urinary symptom. Thus, a person with just frequency or urgency would be excluded from a diagnosis. Secondly, they strongly encourage the exclusion of confusable diseases through an extensive and expensive series of tests including (A) a medical history and physical exam, (B) a dipstick urinalysis, various urine cultures, and a serum PSA in men over 40, (C) flowmetry and post-void residual urine volume by ultrasound scanning and (D) cystoscopy. A diagnosis of IC/BPS would be confirmed with a hydrodistention during cystoscopy with biopsy.They also propose a ranking system based upon the physical findings in the bladder. People would receive a numeric and letter based score based upon the severity of their disease as found during the hydrodistention. A score of 1–3 would relate to the severity of the disease and a rating of A–C represents biopsy findings. Thus, a person with 1A would have very mild symptoms and disease while a person with 3C would have the worst possible symptoms. Widely recognized scoring systems such as the OLeary Sant symptom and problem score have emerged to evaluate the severity of IC symptoms such as pain and urinary symptoms. Differential diagnosis
The symptoms of IC/BPS are often misdiagnosed as a urinary tract infection.
Tangier disease  or hypoalphalipoproteinemia is an extremely rare inherited disorder characterized by a severe reduction in the amount of high density lipoprotein (HDL), often referred to as "good cholesterol", in the bloodstream. Worldwide, approximately 100 cases have even been identified.The disorder was originally discovered on Tangier Island off the coast of Virginia, but has now been identified in people from many different countries. Signs and symptoms
Individuals that are homozygotes for Tangiers disease develop various cholesterol ester depositions. These are especially visible in the tonsils, as they may appear yellow/orange. The cholesterol esters may also be found in lymph nodes, bone marrow, the liver and spleen.Due to the cholesterol ester depositions the tonsils may be enlarged. Hepatosplenomegaly (enlarged liver and spleen) is common.Neuropathy and cardiovascular disease are the most devastating developments caused by Tangiers disease. Genetics
Mutations to chromosome 9q31 lead to a defective ABCA1 transporter. These mutations prevent the ABCA1 protein from effectively transporting cholesterol and phospholipids out of cells for pickup by ApoA1 in the bloodstream. This inability to transport cholesterol out of cells leads to a deficiency of high-density lipoproteins in the circulation, which is a risk factor for coronary artery disease. Additionally, the buildup of cholesterol in cells can be toxic, causing cell death or impaired function. These combined factors lead to the signs and symptoms of Tangier disease.This condition is inherited in an autosomal recessive pattern, meaning that for the phenotype to appear, two copies of the gene must be present in the genotype.