When to act if empyema suspected?

Ok, here is my understanding from reading UpToDate:

Parapneumonic effusion seen on chest xray can be further characterized with ultrasound which can see loculation vs masses and can help the choice of where to do the thoracentesis. If loculations are seen with U/S, or if the ultrasound is inconclusive, a CT with IV contrast is the best imaging modality to characterize an empyema but may not be needed in all cases.

They provided some advice for when to "drain the effusion" which I assumed meant placement of a chest tube or full theraputic thoracentesis because some of the criteria for draining the effusion depended on characteristics of the pleural fluid with would have to be obtained from a diagnostic thoracentesis.
1) if CXR shows 2) if CXR shows >10mm of layering on decubitus but less than 1/2 of the hemithorax then a diagnostic thoracentesis should be done.
- if negative cultures/gram stain AND pH>7.2 then no drainage of the effusion needed.
3) Indications for drainage of effusion (any of the following):
- large parapneumonic effusion (>1/2 hemithorax)
- loculations (seen on CXR, confirmed with either CT or US)
- Thickened parietal pleura (seen on CT)
- positive culture/gram stain
- positive pus found on throacentesis
- pH

These are all based on trying to determine if the effusion is an uncomplicated parapneumonic effusion, complicated parapneumonic effusion or empyema.
- Uncomplicated: exudate with no bacteria/pus/loculation; not requiring drainage
- Complicated: exudate with bacterial invasion into pleural space, increased neutrophils, decreased pH, decreased glucose, can be loculated but no gram stain or culture seen; requires drainage
- Empyema: complicated effusion plus pus, positive gram stain or positive culture; requires drainage.