1972), a pleural effusion is likely exudative if at least one of the following exists:
The ratio of pleural fluid protein to serum protein is greater than 0.5
The ratio of pleural fluid LDH and serum LDH is greater than 0.6
Pleural fluid LDH is greater than 0.6  or 2⁄3 times the normal upper limit for serum. Different laboratories have different values for the upper limit of serum LDH, but examples include 200 and 300 IU/l.The sensitivity and specificity of Lights criteria for detection of exudates have been measured in many studies and are usually reported to be around 98% and 80%, respectively. This means that although Lights criteria are relatively accurate, twenty percent of patients that are identified by Lights criteria as having exudative pleural effusions actually have transudative pleural effusions. Therefore, if a patient identified by Lights criteria as having an exudative pleural effusion appears clinically to have a condition that usually produces transudative effusions, additional testing is needed. In such cases, albumin levels in blood and pleural fluid are measured. If the difference between the albumin level in the blood and the pleural fluid is greater than 1.2 g/dL (12 g/L), this suggests that the patient has a transudative pleural effusion. However, pleural fluid testing is not perfect, and the final decision about whether a fluid is a transudate or an exudate is based not on chemical analysis of the fluid, but an accurate diagnosis of the disease that produces the fluid.
By the 1980s, however, viewing PMS in a social context had begun to take place. Alternative views
Some supporters of PMS as a social construct believe PMDD and PMS to be unrelated issues: according to them, PMDD is a product of brain chemistry, and PMS is a product of a hypochondriatic culture, i.e. a culture-bound syndrome. Most studies on PMS and PMDD rely solely on self-reporting. According to sociologist Carol Tavris, Western women are socially conditioned to expect PMS or to at least know of its existence, and they, therefore, report their symptoms accordingly. The anthropologist Emily Martin argues that PMS is a cultural phenomenon that continues to grow in a positive feedback loop, and thus is a social construction that contributes to learned helplessness or convenient excuse. Tavris says that PMS is blamed as an explanation for rage or sadness. The decision to call PMDD an illness has been criticized as inappropriate medicalization. In both cases, they are referring to the emotional aspects, not the normal physical symptoms that are present. See also
Menstrual leave

References
External links

U.S. Department of Health & Human Services
Direct Online Health Encyclopaedia: Premenstrual syndrome (UK) at NHS
"Premenstrual Syndrome (PMS) (Premenstrual Tension)" at Merck Manual