Free CSPT Practice Test: 60 Questions With Answers

B. Sterile 70% IPA goes on the work surface immediately before compounding and at least every 30 minutes when a process takes 30 minutes or less. When a process runs longer than 30 minutes, USP <797> says compounding must not be disrupted; the surface is disinfected right after. A breaks the no-disruption rule. C skips the required applications. D invents an interval and interrupts the work.

Source: USP <797>, as reproduced by WA DOH 690-296 — §7, item 83.

C. USP <797> Table 13 sets aseptically processed Category 2 CSPs made only from sterile components, without sterility testing, at 4 days room temperature, 10 days refrigerated, and 45 days frozen. 12 hours is the Category 1 room-temperature limit. 1 day is the room-temperature limit when any starting component is nonsterile. 10 days is this CSP's refrigerated limit.

Source: USP <797>, as reproduced by WA DOH 690-296 — §14.3, Tables 12–13, items 132–133.

A. An ISO Class 7 room needs at least 30 total HEPA-filtered ACPH, and at least 15 of those must come from the HVAC through ceiling HEPA filters. PEC air may count toward the total (if it does, the PEC can't be turned off except for maintenance). Here, 18 + 10 = 28, so the room falls short. B satisfies only the HVAC part. C is the ISO Class 8 minimum. D is wrong because USP allows PEC air to contribute.

Source: USP <797>, as reproduced by WA DOH 690-296 — §4.2.4, items 50–51.

B. Concentration: 25,000 units ÷ 250 mL = 100 units/mL. Rate: 1,200 units/hr ÷ 100 units/mL = 12 mL/hr. D comes from using 10 units/mL. A drops a factor of ten. C divides 1,200 by 25. Heparin is on ISMP's high-alert list, which is why an independent check of this math matters in practice.

Source: Castleport arithmetic (shown above); ISMP high-alert list update, Jan 11, 2024 — p. 1–3.

C. USP <797> Table 1 sets gloved fingertip and thumb action levels at more than 0 cfu after garbing and more than 3 cfu after media-fill testing, both counted as the total from both hands. Four exceeds three. A judges each hand separately. B invents a limit. D applies the after-garbing level to a post-media-fill sample. A failure in the media fill, the fingertip sample, or the surface sample fails the whole aseptic manipulation competency.

Source: USP <797>, as reproduced by WA DOH 690-296 — §2.3, Table 1, items 17 and 20.

B. The immediate-container label must show, at minimum, an internal identification number, the active ingredients and their amounts, storage conditions if other than controlled room temperature, the BUD, the dosage form, the total amount if not obvious, and a single-dose or multiple-dose statement. Component lot numbers (A) and a way to identify who compounded and verified the CSP (D) belong in the compounding record, not on the label. The room's ISO class (C) isn't a labeling requirement.

Source: USP <797>, as reproduced by WA DOH 690-296 — §11.2 and §13, items 118 and 126.

D. Anterooms that open into negative-pressure buffer rooms must be at least ISO Class 7, so the air drawn into the hazardous-drug room is as clean as the room itself. ISO Class 8 (B) is the minimum only for anterooms serving positive-pressure buffer rooms. ISO Class 5 (A) is the PEC standard. An unclassified space (C) doesn't qualify.

Source: USP <797>, as reproduced by WA DOH 690-296 — §4.1.2, item 33; USP <800>, as reproduced by WA DOH 690-370 — §5.3.2, item 45.

A. ISMP names potassium chloride for injection concentrate, one of six drugs from its original 1989 list that are still on it. For sodium chloride, ISMP lists only concentrations greater than 0.9% (hypertonic saline), so B isn't on it. Neither ondansetron nor cefazolin is named. "High-alert" means a heightened risk of significant harm when the drug is used in error.

Source: ISMP high-alert list update, Jan 11, 2024 — p. 1–3.

B. Critical sites such as vial stoppers, ampule necks, and IV bag septums are wiped with sterile 70% IPA inside the PEC, and the alcohol must dry before anyone punctures a stopper or breaks an ampule. Puncturing while wet (A) skips the required dry time. Fanning (C) disturbs the clean airflow over the critical site. Nonsterile gauze (D) recontaminates it.

Source: USP <797>, as reproduced by WA DOH 690-296 — §8.3, item 94.

C. A 50% (w/v) solution contains 50 g per 100 mL, or 0.5 g/mL. 25 g ÷ 0.5 g/mL = 50 mL. D multiplies instead of dividing. B halves 25 without converting to a concentration. A treats 50% as 5 g/mL.

Source: Castleport arithmetic (shown above).

A. USP <797> Table 7 sets viable air action levels at more than 1 cfu for ISO Class 5, more than 10 cfu for ISO Class 7, and more than 100 cfu for ISO Class 8. Eight doesn't trigger action, but USP also requires regular, documented review of sampling data to catch trends. B borrows the ISO Class 5 level. C invents one. D is wrong because the count is compared with the action level directly.

Source: USP <797>, as reproduced by WA DOH 690-296 — §6.1 and §6.2.3, Table 7, items 73 and 78.

D. USP <797> lists conjunctivitis, along with rashes, recent tattoos, oozing sores, and active respiratory infections, as conditions that must be reported to the designated person. That person may allow accommodations only if the CSP and environment won't be affected, and the accommodation must be documented. A and C skip the report. B invents a fixed exclusion period USP doesn't set.

Source: USP <797>, as reproduced by WA DOH 690-296 — §3, item 21.

C. A thawed CSP must not be refrozen, storage time must not exceed the original BUD for the labeled storage condition, and BUDs are never added together across conditions. A and B break those rules. D contradicts USP's instruction to thaw under appropriate conditions; its own example of what not to do is heating in a microwave.

Source: USP <797>, as reproduced by WA DOH 690-296 — §14.2.4, items 129–130.

A. The immediate-use exemption applies only when every listed condition is met, including no more than 3 different sterile products and administration beginning within 4 hours of the start of preparation. Four products fails that condition, so the Category 1, 2, or 3 requirements apply. B understates the limit. C and D aren't conditions of the exemption; it has its own conditions for aseptic technique, training, compatibility, and labeling.

Source: USP <797>, as reproduced by WA DOH 690-296 — §1.3, item 3.

C. USP <800> requires sterile hazardous drugs to be compounded in an externally vented containment PEC that provides ISO Class 5 or better air, such as a Class II or III BSC or a compounding aseptic containment isolator (CACI), placed in a C-SEC. It states that an LAFW or a CAI must not be used to compound an antineoplastic hazardous drug, which rules out A and B. A CVE (D) is named for nonsterile hazardous-drug compounding, not among the ISO Class 5 sterile options.

Source: USP <800>, as reproduced by WA DOH 690-370 — §5.3.1–5.3.2, items 33–41.

C. Use C1 × V1 = C2 × V2: 23.4% × V1 = 3% × 100 mL, so V1 = 300 ÷ 23.4 = 12.82 mL, or about 12.8 mL, with the rest of the 100 mL made up with diluent. B divides 23.4 by 3. A and D confuse a concentration with a volume. Both products are sodium chloride stronger than 0.9%, which ISMP lists as high-alert.

Source: Castleport arithmetic (shown above); ISMP high-alert list update, Jan 11, 2024 — p. 1–3.

B. USP <800> requires two pairs of chemotherapy gloves for compounding hazardous drugs. They must meet ASTM D6978 and be powder-free, because powder can spread and hold drug residue, and for sterile compounding the outer pair must be sterile. USP adds that chemotherapy gloves should be changed every 30 minutes unless the manufacturer says otherwise, and right away if torn, punctured, or contaminated. A and D are single pairs. C uses powdered gloves.

Source: USP <800>, as reproduced by WA DOH 690-370 — §7 and §7.1, items 54–55.

D. USP <800> bars pneumatic tubes for any liquid hazardous drug and any antineoplastic hazardous drug because of the risk of breakage and contamination. Hazardous drugs travel in containers that minimize breakage or leakage and stay clearly labeled for special handling. A and B still use the tube. C treats a label as a substitute for safe transport.

Source: USP <800>, as reproduced by WA DOH 690-370 — §11.1 and §11.3, items 85 and 90–92.

B. A single-dose vial entered or punctured only in ISO Class 5 or cleaner air may be used for up to 12 hours after first entry, as long as labeled storage conditions are kept. 08:00 + 12 hours = 20:00. C gives 24 hours. D treats a punctured single-dose vial like an unopened one. Two related rules: opened single-dose ampules must not be stored at all, and a multiple-dose container may be used up to 28 days after first entry unless its labeling says otherwise.

Source: USP <797>, as reproduced by WA DOH 690-296 — §15.1–15.2, items 140–141.

A. Sterilizing filters must be sterile, depyrogenated, 0.22 µm or smaller, appropriate for pharmaceutical use, and put through the manufacturer's recommended integrity test, such as a post-use bubble point test. A 1.2 µm filter (B) appears in USP only as a prefilter to remove gross particulates. A 5 µm filter needle (C) isn't a sterilizing filter. USP bars filters labeled for laboratory use only (D).

Source: USP <797>, as reproduced by WA DOH 690-296 — §10.2, item 108.

D. The pressure differential between the anteroom and the unclassified area must not be less than 0.020 inch water column, so only 0.025 meets it. USP also requires a device that monitors the differential continuously, with results reviewed and documented at least daily on days compounding happens.

Source: USP <797>, as reproduced by WA DOH 690-296 — §4.2.5, items 52–54.

C. Anyone entering a compounding area must wash hands and forearms up to the elbows with soap and water before compounding. USP bars brushes (A), refilling or topping off disposable soap containers (B), and hand dryers (D). Hands are then sanitized with alcohol-based hand rub before sterile gloves go on.

Source: USP <797>, as reproduced by WA DOH 690-296 — §3.2, item 24.

B. Flow rate: 1,000 mL ÷ 8 hr = 125 mL/hr. Drip rate: 125 mL/hr × 15 gtt/mL ÷ 60 min/hr = 31.25, which rounds to 31 gtt/min. A uses a 10 gtt/mL set. C uses a 20 gtt/mL set. D is the flow rate in mL/hr, mislabeled as drops per minute.

Source: Castleport arithmetic (shown above).

A. USP <797> Table 13 sets aseptically processed Category 2 CSPs made from one or more nonsterile components, without sterility testing, at 1 day room temperature, 4 days refrigerated, and 45 days frozen. B is the Category 1 refrigerated limit. C is the refrigerated limit when only sterile components are used. D is the frozen limit, and also the refrigerated limit once sterility testing is performed and passed.

Source: USP <797>, as reproduced by WA DOH 690-296 — §14.3, Table 13, item 133.

C. USP <797> requires a compounding record (CR) for every Category 1, 2, and 3 CSP. A master formulation record (MFR), the detailed "recipe" for preparing a CSP, is required when the CSP uses nonsterile ingredients or is prepared for more than one patient. Neither applies here. A and B add a document USP doesn't require in this case, though a facility's own procedures may. D drops the CR entirely.

Source: USP <797>, as reproduced by WA DOH 690-296 — §11.1–11.2, items 114 and 117.

D. Before items go into the clean side of an anteroom, a pass-through, or an SCA, gloved personnel must wipe them with a sporicidal disinfectant, EPA-registered disinfectant, or sterile 70% IPA using low-lint wipers, without damaging packaging or making the label unreadable. Corrugated or uncoated cardboard (A) isn't allowed in classified areas or SCAs. Food, explicitly including mints and gum (B), is prohibited. Earbuds and headphones (C) must not be worn.

Source: USP <797>, as reproduced by WA DOH 690-296 — §3.1, §4.5, §8.1, items 22–23, 61, 92.

D. USP <800> requires deactivation residue to be removed by decontaminating the surface. It specifically says sodium hypochlorite must be neutralized with sodium thiosulfate or followed by an agent that removes it (for example, sterile alcohol, sterile water, germicidal detergent, or a sporicidal agent) to prevent corrosion. A leaves corrosive residue. B puts nonsterile water on a sterile compounding surface. C adds more residue.

Source: USP <800>, as reproduced by WA DOH 690-370 — §15.1, item 121.

A. For people compounding Category 3 CSPs, USP <797> requires the aseptic manipulation competency initially and at least every 3 months. Every 6 months (B) is the interval for Category 1 and 2 compounders. Every 12 months (C) is for people who directly oversee compounders but don't compound. D ignores the ongoing requirement.

Source: USP <797>, as reproduced by WA DOH 690-296 — §2.3, item 13.

B. A CSP's BUD must not exceed the shortest remaining expiration date of any commercially available starting component. The chapter's 10-day limit is a ceiling, not a guarantee, so the 6-day vial controls. C adds the two numbers. D is the room-temperature limit for this type of CSP.

Source: USP <797>, as reproduced by WA DOH 690-296 — §14.3, item 131.

D. Alligation: 50 − 20 = 30 parts of the 10% solution; 20 − 10 = 10 parts of the 50% solution; 40 parts total. 50% solution: 500 mL × 10/40 = 125 mL. 10% solution: 500 mL × 30/40 = 375 mL. Check: (125 × 0.50) + (375 × 0.10) = 62.5 + 37.5 = 100 g in 500 mL, which is 20%. C is the volume of 10% solution. A and B don't balance.

Source: Castleport arithmetic (shown above).

A. A LAFS used for Category 2 or 3 CSPs must sit inside a cleanroom suite with an ISO Class 7 or better buffer room and an ISO Class 8 or better anteroom. Only a facility compounding Category 1 CSPs alone may put its PEC in an unclassified SCA (B). A certified PEC (C) doesn't replace the required room. D lacks both the ISO Class 7 buffer room and the anteroom.

Source: USP <797>, as reproduced by WA DOH 690-296 — §4.1.2 and §4.2.3, items 33 and 45.

D. Skin must not be exposed inside the ISO Class 5 PEC, so gloves must not be donned or doffed there in a way that exposes bare hands. A torn glove is replaced, just not inside the PEC. A, B, and C are all required or allowed: sterile gloves are donned in a classified room or SCA, soiled garb is replaced right away, and sterile 70% IPA goes on gloves immediately before compounding and regularly throughout.

Source: USP <797>, as reproduced by WA DOH 690-296 — §3.2–3.3, items 25, 27, 29, 32.

C. USP <800> requires antineoplastic hazardous drugs and all hazardous-drug active ingredients to be unpacked in an area that is neutral/normal or negative pressure relative to surrounding areas, and bars unpacking in sterile compounding areas or positive-pressure areas (A and B). Chemotherapy gloves are required when unpacking, but they don't replace the location rule (D).

Source: USP <800>, as reproduced by WA DOH 690-370 — §5.1 and §10, items 17–18 and 76–78.

D. USP <797> requires endotoxin testing for Category 2 injectable CSPs compounded from one or more nonsterile components and assigned a BUD that requires sterility testing, and for Category 3 injectable CSPs made from nonsterile components. Category 2 nonsterile-component CSPs with shorter BUDs should be tested. Nonsterile starting materials are the reason, so A, B, and C, all made from sterile components, fall outside the requirement.

Source: USP <797>, as reproduced by WA DOH 690-296 — §12.3, item 124.

B. USP <800> requires the C-SEC to be externally vented, physically separated, and held at negative pressure between 0.01 and 0.03 inch water column relative to all adjacent areas, so air flows in rather than carrying drug out. A is the positive-pressure standard for a non-hazardous anteroom. C and D fall outside the specified range.

Source: USP <800>, as reproduced by WA DOH 690-370 — §5.3, items 23–24.

A. USP <800>'s hazard communication program requires an SDS for each hazardous chemical used (29 CFR 1910.1200), readily accessible to staff in their work areas during each shift. The compounding record (B) documents one preparation, the master formulation record (C) is a preparation recipe, and the certification report (D) documents engineering-control testing.

Source: USP <800>, as reproduced by WA DOH 690-370 — §8, items 66–68.

C. CSPs made with a filter that failed integrity testing must be discarded or, after the cause is investigated and an appropriate filter selected, refiltered for sterilization not more than one more time. A and B release a CSP whose sterility wasn't established. D ignores the one-additional-time limit.

Source: USP <797>, as reproduced by WA DOH 690-296 — §10.2, item 109.

B. 40 mEq ÷ 2 mEq/mL = 20 mL. D multiplies instead of dividing. C assumes 1 mEq/mL. Potassium chloride concentrate is on ISMP's high-alert list, so in practice this volume is exactly the kind of number that gets an independent check before it goes into a bag.

Source: Castleport arithmetic (shown above); ISMP high-alert list update, Jan 11, 2024 — p. 1–3.

A. For Category 1 and 2 compounding, USP <797> requires surface sampling of all classified areas and connecting pass-throughs at least monthly. Weekly (B) is the Category 3 requirement. Every 6 months (C) is the viable air sampling interval for Category 1 and 2. D isn't a USP <797> surface-sampling interval.

Source: USP <797>, as reproduced by WA DOH 690-296 — §6.2.1 and §6.3.1, items 76 and 80.

B. A media fill swaps every component for soybean–casein digest medium, a microbial growth medium, so any contamination introduced during the simulated process grows and shows up. The simulation should reproduce the most difficult and challenging aseptic procedures the person performs. Water (A) and saline (C) wouldn't reveal contamination. IPA (D) would kill it.

Source: USP <797>, as reproduced by WA DOH 690-296 — §2.3, items 14–15.

C. Compounding personnel must assess ACD accuracy before first use and again on each day the device is used to compound CSPs, keep a daily record of the measurements, and take corrective action if results fall outside the manufacturer's specification. A, B, and D all leave days of use unchecked.

Source: USP <797>, as reproduced by WA DOH 690-296 — §9.1, item 96.

A. Protamine sulfate injection is indicated for the treatment of heparin overdosage. Its label also warns that too-rapid administration can cause severe low blood pressure and anaphylactoid reactions. Phytonadione, naloxone, and flumazenil aren't labeled to reverse heparin. All four appear on PTCB's CSPT Exam Medications List, which is why pairing a drug with its reversal agent is worth drilling.

Source: DailyMed, protamine sulfate injection label — Indications and Usage; Warnings.

D. In a cleanroom suite, the hand-hygiene sink may be inside the anteroom on either side, or outside the anteroom in a clean space. The buffer room must not contain any plumbed water source, including sinks, eyewashes, showers, and floor drains, which rules out A and C. The anteroom must not contain floor drains (B). The 1-meter spacing in A is the rule for a sink serving a segregated compounding area, not a buffer room.

Source: USP <797>, as reproduced by WA DOH 690-296 — §4.4, item 59.

B. Infusion time = volume ÷ rate = 300 mL ÷ 150 mL/hr = 2 hours. The 1.5 g dose doesn't enter the time calculation; D multiplies it by 3. A and C misread the rate.

Source: Castleport arithmetic (shown above).

A. The minimum garb for Category 1 and 2 CSPs is a low-lint garment with snug sleeves and an enclosed neck, low-lint shoe covers, a low-lint cover for the head that covers hair and ears (plus a facial-hair cover if needed), a low-lint face mask, and sterile powder-free gloves. A cloth lab coat (B) isn't a low-lint garment. The gloves must be powder-free (C). Goggles (D) aren't on the minimum list; they come in where splashes are a risk, such as some hazardous-drug work.

Source: USP <797>, as reproduced by WA DOH 690-296 — §3.3, item 28.

C. Beyond routine frequencies, sampling is required with certification of new facilities and equipment, after any servicing, in response to identified problems (such as positive sterility tests), in response to trends (such as repeated positive fingertip samples or failed media fills), and after changes that could affect the environment, such as a new cleaning agent. B names one trigger but not the only one. A and D aren't triggers.

Source: USP <797>, as reproduced by WA DOH 690-296 — §6.1, item 75.

D. Cleaning, disinfecting, and sporicidal agents used inside the PEC must be sterile, and when concentrated agents are diluted for PEC use, sterile water must be used. Tap or sink water (A, B) is nonsterile. Saline (C) isn't the diluent USP names.

Source: USP <797>, as reproduced by WA DOH 690-296 — §7.1.1, item 88.

B. The label says the solution is sensitive to certain wavelengths of light, so the diluted solution is protected with the supplied opaque sleeve, foil, or other opaque material, and it isn't necessary to cover the drip chamber or tubing. Properly protected, the freshly diluted solution is stable for 24 hours. The concentrate is not for direct injection; it must be diluted in 5% dextrose first. A ignores the requirement. C goes beyond what the label requires. D swaps in a storage condition the label doesn't give.

Source: DailyMed, sodium nitroprusside injection label — Description; Dosage and Administration; carton label.

C. Cleaning moves from clean to dirty areas. USP <797> says the same floor mop may be used in both the buffer room and the anteroom, but only in that order: buffer room first. A drags dirtier-area contamination into the cleaner room. B isn't an exception USP allows. D is stricter than the chapter.

Source: USP <797>, as reproduced by WA DOH 690-296 — §7, item 86.

A. When a CSP will be stored frozen, USP <797> requires a container closure system that can take the physical stress of freezing without breaking or cracking. The chapter doesn't require a particular material or color (B, C, D). Once thawed, the CSP must not be refrozen.

Source: USP <797>, as reproduced by WA DOH 690-296 — §14.2.4, items 128–129.

D. In a PEC, HEPA-filtered air must reach critical sites at a velocity that sweeps particles away from them. First air is that air coming straight off the HEPA filter, before it passes over anything else. A hand upstream of the stopper puts itself in that path, so the air reaching the critical site has already passed over the glove. Sterile IPA on gloves (C) lowers contamination but doesn't restore first air. A and B aren't the concern.

Source: USP <797>, as reproduced by WA DOH 690-296 — §4.2.2 and §4.2.3, items 43 and 45.

A. 10% (w/v) = 10 g per 100 mL, or 0.1 g/mL. 60 g ÷ 0.1 g/mL = 600 mL. B and C shift the decimal. D is a common bag size, not the answer.

Source: Castleport arithmetic (shown above).

B. Classified areas and PECs are certified initially and recertified at least every 6 months, covering airflow testing, HEPA filter integrity testing, total particle counts under dynamic conditions, and dynamic airflow smoke-pattern tests. Recertification is also required after redesign, construction, replacement or relocation of a PEC, or room changes that could affect airflow. A, C, and D don't match that schedule.

Source: USP <797>, as reproduced by WA DOH 690-296 — §5, items 66–67.

C. Unpreserved aqueous topical and ophthalmic preparations carry a high risk of microbial growth once opened. USP <797> waives antimicrobial effectiveness testing only if the CSP is Category 2 or 3, for a single patient, and labeled to be discarded 24 hours after opening at room temperature or 72 hours after opening under refrigeration. 28 days (A) is the multiple-dose limit that applies with passing antimicrobial effectiveness testing. B and D aren't the labeled limits.

Source: USP <797>, as reproduced by WA DOH 690-296 — §14.5, items 137 and 139.

D. Components are stored under the temperature, humidity, and light conditions their monographs or manufacturers specify. Temperature is monitored manually at least once daily on open days or with a continuous recording device, documented in a retrievable log, and the monitoring equipment is calibrated as the manufacturer recommends or every 12 months. A, B, and C leave too many days unchecked.

Source: USP <797>, as reproduced by WA DOH 690-296 — §9.3.4, item 105.

B. USP <800> says a plastic-backed preparation mat should be placed on the containment PEC's work surface, changed immediately if a spill occurs and regularly during use, and discarded at the end of the daily compounding activity. A and D keep a mat that may carry drug residue. C contradicts the chapter.

Source: USP <800>, as reproduced by WA DOH 690-370 — §13, item 99.

C. The paclitaxel label explains that DEHP [di-(2-ethylhexyl) phthalate] can leach from PVC infusion bags or sets. To limit patient exposure, diluted solutions are stored in glass or polypropylene bottles or in polypropylene or polyolefin bags and given through polyethylene-lined sets, with an in-line filter of 0.22 microns or smaller. A, B, and D aren't the reasons the label gives.

Source: DailyMed, paclitaxel injection label — Dosage and Administration; Preparation note.

D. Every CSP is visually inspected at the end of compounding. When a CSP won't be released or dispensed the day it's made, it must be inspected again immediately before release, because defects such as precipitation, cloudiness, or leakage can develop in storage. Defects pointing to sterility or stability problems are investigated. A skips the second check. B and C aren't what USP requires here, and a BUD can't be extended just by relabeling.

Source: USP <797>, as reproduced by WA DOH 690-296 — §12.1, items 120–121.

A. USP <797> says surface sampling should happen at the end of a compounding activity or shift, before cleaning and disinfection, so results show real working conditions. The sampling devices contain growth media with neutralizers (such as lecithin and polysorbate 80) to counter leftover disinfectant, and the sampled area is cleaned afterward. B and C would understate contamination. D ignores the routine sampling schedule.

Source: USP <797>, as reproduced by WA DOH 690-296 — §6.1 and §6.3.2, items 75 and 81.

D. Injectable preparations that contain nonsterile components, or that contact nonsterile devices during compounding, must be sterilized within 6 hours after preparation is complete. The time limit minimizes the buildup of bacterial endotoxins. A, B, and C aren't the USP limit.

Source: USP <797>, as reproduced by WA DOH 690-296 — §10, item 106.